feat(renderer): App.tsx renders AppShell

- Phase 1: Foundation (shadcn, deps, lib utils, motion presets, theme)
- Phase 2: App shell + resizable panes
- Phase 3: Editor (CodeMirror 6 + immer store)
- Phase 4: Preview (marked + KaTeX + mermaid + scroll sync)
- Phase 5: File tree + tabs
- Phase 6: Native menus + toolbar
- Phase 7: Modals (export, settings, about, confirm)
- Phase 8: Toasts (sonner)
- Phase 9: Advanced tools (zen, repl, ascii, table, print, word)
- Phase 10: Polish + delete legacy renderer

Phases 1-4 are fully fleshed out (60+ TDD tasks with working code).
Phases 5-9 are sketched with the same TDD pattern; detailed
steps will be expanded at execution time following the conventions
established in Phases 1-4.

components.json

@@ -0,0 +1,20 @@
+{
+  "$schema": "https://ui.shadcn.com/schema.json",
+  "style": "new-york",
+  "rsc": false,
+  "tsx": true,
+  "tailwind": {
+    "config": "tailwind.config.js",
+    "css": "src/renderer/styles/globals.css",
+    "baseColor": "neutral",
+    "cssVariables": true,
+    "prefix": ""
+  },
+  "aliases": {
+    "components": "@/components",
+    "ui": "@/components/ui",
+    "lib": "@/lib",
+    "hooks": "@/hooks"
+  },
+  "iconLibrary": "lucide"
+}

docs/superpowers/specs/2026-06-05-react-ui-redesign-design.md

@@ -0,0 +1,361 @@
+# MarkdownConverter — React + shadcn/ui UI Redesign
+
+**Date:** 2026-06-05
+**Status:** Design (awaiting user approval)
+**Branch:** `react-electron`
+**Author:** Brainstormed with user via superpowers:brainstorming
+
+## Summary
+
+Replace the legacy vanilla JS renderer (`src/renderer.js` is 213 KB; `src/styles.css` is 74 KB) with a modern React 19 + Vite + TypeScript + shadcn/ui renderer that achieves visual feature parity while delivering a Polished + Glassy (Raycast/Arc-style) aesthetic. The Electron main process, preload bridge, and IPC contracts stay unchanged. Work proceeds via vertical slices — each PR ships a demoable feature.
+
+## Goals
+
+1. Replace every render-time feature of the legacy renderer with an idiomatic React + shadcn/ui implementation.
+2. Adopt the "Polished + Glassy" visual language (subtle shadows, 8–12 px radii, gradient accents, gentle depth) on top of the existing ConcreteInfo brand tokens and design system.
+3. Use a single component foundation (shadcn/ui) and a single motion library (Motion / Framer Motion) to keep the dependency surface narrow and the design coherent.
+4. Keep the main process, preload, and IPC contracts untouched. The renderer is the only surface being rewritten.
+5. Keep the app runnable at every commit. No "big bang" merge.
+
+## Non-Goals
+
+- Migrating the main process to TypeScript (out of scope for this spec).
+- Adding new features the legacy renderer does not have (plugin system, AI features, etc. — those are future specs).
+- Replacing Pandoc/FFmpeg/ImageMagick orchestration.
+- Changing the packaging pipeline (electron-builder config stays).
+- Replacing the CodeMirror 6 editor — it is the right tool and is already wired up.
+
+## Decisions Locked During Brainstorming
+
+| Decision | Choice | Why |
+|---|---|---|
+| Scope | Full feature parity with legacy renderer | User-selected option. Renderer is one cohesive surface; splitting it across specs would force premature contracts. |
+| Visual style | **B — Polished + Glassy** (Raycast/Arc aesthetic) | "Fancy" comes from elevation, gradient accents, and material depth — not over-designed visuals. |
+| Layout | **2 — IDE-style** (equal editor/preview, draggable divider, collapsible sidebar) | Power-user markdown apps converge on this. Draggable divider + keyboard reset. |
+| Modal patterns | **A (Centered Dialog), B (Right Side-Sheet), D (Toasts)** | No command palette. |
+| Command palette | **No** — full menus, no ⌘K | Power users can use the OS-level launcher. App stays focused on writing. |
+| Animation | **Motion (Framer Motion)** | Best for layout transitions, modal/drawer enter/exit, drag. Sparingly used. |
+| Component library | **shadcn/ui** | Tailwind + Radix primitives, copy-paste ownership, perfect fit for the "glassy" aesthetic and the HSL-CSS-variable foundation that is already in place. |
+| Implementation strategy | **Vertical slices** — one feature end-to-end per PR | App stays runnable. Each PR is reviewable. |
+
+## Defaults (Used Unless Overridden Later)
+
+| Item | Default | Why |
+|---|---|---|
+| State management | Zustand (already in deps) + Immer for nested patches | Already in `package.json`; perfect for editor state. |
+| Theming | shadcn `next-themes`, dark default + light, system-aware | shadcn canonical pattern. Brand colors already in CSS vars. |
+| Icons | `lucide-react` (already in deps) | 1000+ tree-shakable icons. |
+| Forms | `react-hook-form` + `zod` | Standard for shadcn forms. |
+| Drag/drop (sortable lists) | `@dnd-kit/core` | De facto React drag lib (file tree reordering, plugin list reorder). |
+| Pane resize (split layout) | `react-resizable-panels` | Canonical React lib for resizable pane groups; handles drag, arrow keys, snap, persisted sizes. |
+| Testing | Vitest + RTL + Playwright (E2E + visual regression) | Standard for React + Electron. |
+| TypeScript | Strict mode (already wired) | Already in deps and `vite.renderer.config.ts`. |
+
+## Architecture
+
+The Electron app keeps its existing process model. Only the renderer is rewritten.
+
+```
+┌──────────────────────────────────────────────────────────┐
+│  Electron Main (UNCHANGED)                                │
+│  - BrowserWindow, IPC handlers, file/fs ops               │
+│  - Pandoc, FFmpeg, ImageMagick orchestration              │
+└────────────┬─────────────────────────────────────────────┘
+             │ contextBridge (UNCHANGED preload.js)
+┌────────────▼─────────────────────────────────────────────┐
+│  React Renderer (REWRITTEN)                                │
+│  ┌────────────────────────────────────────────────────┐  │
+│  │  AppShell (layout)                                  │  │
+│  │  ├─ MenuBar (native)                                │  │
+│  │  ├─ AppHeader (logo, breadcrumbs, theme toggle)     │  │
+│  │  ├─ TabBar (open files)                             │  │
+│  │  ├─ Toolbar (formatting)                            │  │
+│  │  ├─ ResizablePaneGroup (sidebar | editor | preview) │  │
+│  │  │   ├─ Sidebar (file tree, outline)                │  │
+│  │  │   ├─ EditorPane (CodeMirror 6)                   │  │
+│  │  │   └─ PreviewPane (marked + KaTeX + Mermaid)      │  │
+│  │  ├─ StatusBar (word count, encoding, cursor pos)    │  │
+│  │  └─ ModalLayer (Dialog, SideSheet, Toaster)         │  │
+│  └────────────────────────────────────────────────────┘  │
+│  ┌────────────────────────────────────────────────────┐  │
+│  │  Feature Modules (each owns UI + state slice)       │  │
+│  │  ├─ editor/    CodeMirror wrapper, syntax, themes   │  │
+│  │  ├─ preview/   markdown→html, KaTeX, Mermaid       │  │
+│  │  ├─ tabs/      open files, dirty state              │  │
+│  │  ├─ sidebar/   file tree, outline, search results   │  │
+│  │  ├─ modals/    export, settings, about, etc.        │  │
+│  │  ├─ tools/     zen, repl, ascii-gen, table-gen      │  │
+│  │  └─ export/    pdf, docx, html, image batch         │  │
+│  └────────────────────────────────────────────────────┘  │
+│  ┌────────────────────────────────────────────────────┐  │
+│  │  Shared Infrastructure                              │  │
+│  │  ├─ stores/  Zustand slices per feature             │  │
+│  │  ├─ hooks/   useFile, useEditor, useTheme, etc.     │  │
+│  │  ├─ lib/     cn, ipc, formatters, validators        │  │
+│  │  ├─ ui/      shadcn primitives: button, dialog…     │  │
+│  │  └─ types/   shared TS types                        │  │
+│  └────────────────────────────────────────────────────┘  │
+└──────────────────────────────────────────────────────────┘
+```
+
+### Architectural Rules
+
+- **Shell components** (`AppHeader`, `TabBar`, `StatusBar`) subscribe only to `useAppStore`.
+- **Feature components** subscribe to their own feature's store.
+- **Cross-feature access** goes through hooks, not direct store imports (e.g., `useFileTree()` wraps `useFileStore`).
+- **Feature modules are self-contained** — each owns its components, its Zustand slice, and its types. Safe to develop in parallel later.
+- **No direct `window.electronAPI` calls** from feature code. All IPC goes through `lib/ipc.ts` for type safety and error normalization.
+
+## State Management
+
+```
+stores/
+├─ useAppStore        // global UI: theme, sidebar, pane sizes, modals open
+├─ useFileStore       // file system: tree, open files, active tab
+├─ useEditorStore     // editor: per-file content, cursor, selection, dirty
+├─ usePreviewStore    // preview: scroll sync, zoom, theme
+├─ useSettingsStore   // user prefs (persisted to electron-store)
+└─ useCommandStore    // menu actions registry, recent actions
+```
+
+**Why slices instead of one mega-store?** Editor content can be megabytes. Keeping it in its own slice lets React avoid re-rendering the preview when only the editor changes — components subscribe with selectors.
+
+**Persistent state** (auto-saved to electron-store via Zustand `persist` middleware): theme, sidebar visibility, last open files, pane divider positions, settings.
+
+**Ephemeral state** (lost on quit): active modal, hover states, search query, current file content (saved to disk on idle).
+
+## Visual Design System
+
+### Color Tokens
+
+The existing `globals.css` HSL variables stay. Additions for the "glassy" aesthetic:
+
+```css
+--shadow-sm: 0 1px 2px rgba(13, 11, 9, 0.06);
+--shadow-md: 0 4px 12px rgba(13, 11, 9, 0.08), 0 0 0 1px rgba(13, 11, 9, 0.04);
+--shadow-lg: 0 12px 32px rgba(13, 11, 9, 0.12), 0 0 0 1px rgba(13, 11, 9, 0.06);
+--shadow-glow-brand: 0 0 24px rgba(229, 70, 31, 0.25);
+
+--glass-bg-light: rgba(255, 255, 255, 0.72);
+--glass-bg-dark:  rgba(13, 11, 9, 0.72);
+--glass-border-light: rgba(255, 255, 255, 0.4);
+--glass-border-dark:  rgba(255, 255, 255, 0.08);
+```
+
+### shadcn Components
+
+Install via `npx shadcn@latest add`:
+
+**Primitives** (need all of these): `button`, `dialog`, `sheet`, `popover`, `tooltip`, `select`, `dropdown-menu`, `tabs`, `separator`, `scroll-area`, `toggle`, `switch`, `slider`, `input`, `textarea`, `label`, `form`, `skeleton`, `sonner`, `command`.
+
+**Composite** (custom-built on top of primitives): `file-tree`, `pane-group`, `divider`, `status-bar`, `menu-bar`, `toast`.
+
+### Typography
+
+- Body: Plus Jakarta Sans 15 px / line-height 1.6
+- Code: JetBrains Mono 13.5 px
+- Display: Barlow Condensed 700/800 — used sparingly (page titles, big metrics)
+- Headings: Plus Jakarta Sans 600/700 with tight letter-spacing
+- Labels (`.label`): Plus Jakarta Sans 500, 12 px, uppercase, 0.05 em letter-spacing
+
+### Motion Choreography
+
+| Element | Motion | Duration | Easing |
+|---|---|---|---|
+| Modal (Dialog A) | Scale 0.96→1, opacity 0→1 | 200 ms | `ease-out` |
+| Side sheet (B) | TranslateX 100%→0, opacity 0→1 | 300 ms | `cubic-bezier(0.16, 1, 0.3, 1)` |
+| Toast | TranslateY 100%→0, opacity | 250 ms | spring(stiffness: 300, damping: 30) |
+| Sidebar toggle | Width 264 px↔72 px, content fade | 250 ms | `ease-in-out` |
+| Divider drag | Live width update | 0 ms | none (instant) |
+| Theme switch | CSS variables, opacity overlay | 300 ms | `ease-in-out` |
+| Tab switch | Underline slide | 200 ms | `ease-out` |
+| Hover (buttons) | `bg` + `shadow` shift | 150 ms | `ease-out` |
+| Focus ring | Outline grow | 100 ms | `ease-out` |
+
+**Rules:** Every motion has a purpose. No gratuitous animation. Respects `prefers-reduced-motion` (Motion handles this automatically).
+
+### Empty / Loading / Error States
+
+Every async surface ships all three. Sonner toasts for ephemeral feedback. Skeleton screens for content areas. Empty-state components with icon + message + primary CTA.
+
+## Modal/Overlay Patterns
+
+| Use case | Pattern | Why |
+|---|---|---|
+| Export (PDF/DOCX/HTML) | A — Centered Dialog | Focused decision, ~3–5 fields, "do one thing" |
+| Settings | B — Right Side-Sheet | Long form, tabbed sections, stays open while editing |
+| Find/Replace | Inline toolbar (not modal) | Always-visible utility |
+| About | A — Centered Dialog | Tiny info dump |
+| Confirm destructive (delete, close unsaved) | A — Centered Dialog | Forces attention |
+| File save error | D — Toast | Non-blocking info |
+| Pandoc/FFmpeg progress | D — Toast → sticky on >3 s | Background work feedback |
+| Plugin manager | B — Right Side-Sheet | Lists + per-item actions |
+| ASCII/Table generators | A — Centered Dialog | Tool-style focused input → output |
+| Print preview | A — Centered Dialog | Full-screen-ish modal overlay |
+| Welcome (first launch) | A — Centered Dialog | One-time onboarding |
+| Word export | A — Centered Dialog | Template selection |
+| Zen mode | Full-viewport toggle (no modal) | Replaces the editor entirely |
+| REPL | Bottom-pinned panel (split-pane) | Persistent terminal-like UI |
+| Quick file open | B — Right Side-Sheet | File tree, search, recent |
+
+### Dialog A Anatomy (Export as example)
+
+```
+┌─ Backdrop (rgba(13,11,9,0.45) + backdrop-blur 4px) ─────────┐
+│                                                            │
+│   ┌──── Modal (max-w-md, rounded-2xl, shadow-lg) ─────┐    │
+│   │ ┌── Header ────────────────────────────────────┐  │    │
+│   │ │ [Icon] Export as PDF                  [×]    │  │    │
+│   │ │ Choose format options                       │  │    │
+│   │ └─────────────────────────────────────────────┘  │    │
+│   │ ┌── Body ──────────────────────────────────────┐  │    │
+│   │ │ Format: [Letter] [A4] [Legal]                │  │    │
+│   │ │ Margins: ────●────                           │  │    │
+│   │ │ ☐ Include table of contents                  │  │    │
+│   │ │ ☐ Embed fonts                                │  │    │
+│   │ └─────────────────────────────────────────────┘  │    │
+│   │ ┌── Footer ────────────────────────────────────┐  │    │
+│   │ │                       [Cancel] [Export →]    │  │    │
+│   │ └─────────────────────────────────────────────┘  │    │
+│   └──────────────────────────────────────────────────┘    │
+│                                                            │
+└────────────────────────────────────────────────────────────┘
+```
+
+### Side-Sheet B Anatomy (Settings as example)
+
+Slides in from right, ~50 % width (max 560 px). Backdrop is `rgba(13,11,9,0.2)` with `backdrop-blur(2 px)` (lighter than dialog — the sheet is the focus). Tab navigation in the sheet header (Editor / Theme / Export / Plugins / About).
+
+### Toast D Anatomy (Sonner)
+
+Stacked bottom-right, max 3 visible. Glass background. Color-coded 3 px left border — success `#1a7a56`, error `#ef4444`, info `#0ea5e9`, warning `#eab308`. Icon + title + description. Optional action button. Auto-dismiss 4 s for success, sticky for error.
+
+## Data Flow (Editor → Preview Pipeline)
+
+```
+User types
+  ↓
+CodeMirror onChange
+  ↓
+useEditorStore.updateContent(tabId, content)  ← debounced 50 ms
+  ↓
+┌─ Persist to electron-store on idle (1 s) ─┐
+│                                            │
+└─ Publish to usePreviewStore (subscribed) ─┘
+  ↓
+marked(content) → sanitized HTML
+  ↓
+PreviewPane renders HTML
+  KaTeX post-processes $...$
+  Mermaid post-processes ```mermaid
+  Highlight.js post-processes ```lang
+  ↓
+useEffect: scroll-sync editor cursor → preview position
+```
+
+**Bidirectional scroll sync:** editor scroll → preview (primary), preview click → editor cursor (secondary). Throttled to 60 fps via `requestAnimationFrame`.
+
+## IPC Contract
+
+The preload bridge stays unchanged. A new `src/renderer/lib/ipc.ts` wraps every channel with TypeScript types and normalizes errors to a discriminated union:
+
+```ts
+type IpcResult<T> =
+  | { ok: true; data: T }
+  | { ok: false; error: { code: string; message: string } };
+
+export const ipc = {
+  file: {
+    open: (): Promise<IpcResult<FileResult>>,
+    read: (path: string): Promise<IpcResult<string>>,
+    write: (path: string, content: string): Promise<IpcResult<void>>,
+    list: (dir: string): Promise<IpcResult<FileEntry[]>>,
+    onChange: (cb: (path: string) => void) => () => void,
+  },
+  export: {
+    pdf: (opts: PdfOptions): Promise<IpcResult<ExportResult>>,
+    docx: (opts: DocxOptions): Promise<IpcResult<ExportResult>>,
+    html: (opts: HtmlOptions): Promise<IpcResult<ExportResult>>,
+    batch: (items: BatchItem[], opts: BatchOptions): Promise<IpcResult<BatchResult>>,
+  },
+  app: {
+    getVersion: (): Promise<IpcResult<string>>,
+    openExternal: (url: string): Promise<IpcResult<void>>,
+    showItemInFolder: (path: string): Promise<IpcResult<void>>,
+  },
+};
+```
+
+## Error Handling
+
+Layered defense — no single failure can crash the app:
+
+1. **IPC errors** → caught in `lib/ipc.ts` wrapper, returned as `IpcResult<T>` discriminated union. Components show toast on error.
+2. **Component errors** → React error boundary per feature area (one for editor, one for preview, one for modals). On error: show inline error UI with "Reload this panel" + "Copy details" actions.
+3. **Async operations** (export, file ops) → loading state on button + toast on completion. Long ops (>2 s) get a sticky toast with cancel.
+4. **Validation errors** (settings, export options) → inline form errors via `react-hook-form` + `zod`. shadcn `Form` component for consistent error display.
+5. **Pandoc/FFmpeg missing** → detected at startup, banner + disable export menu items. Don't surprise-fail at export time.
+
+## Testing Strategy
+
+- **Unit (Vitest):** stores, hooks, lib utilities, formatters, validators
+- **Component (Vitest + RTL):** shadcn wrappers, dialog interactions, sidebar toggle, divider drag, theme toggle
+- **Integration (Vitest + RTL):** editor ↔ preview flow, file open → tab add → content display, settings change persists
+- **E2E (Playwright):** app launches, file opens, markdown renders, export to PDF works
+- **Visual regression (Playwright snapshots):** locked-in screenshots for header, sidebar, dialogs, toasts — catch accidental style drift
+- **Target coverage:** stores/hooks/lib ≥ 90 %, components ≥ 75 %, E2E covers all critical paths
+
+## Accessibility (WCAG 2.1 AA)
+
+Baked in via shadcn + Radix:
+
+- All dialogs focus-trap, Esc to close, return focus to trigger
+- All interactive elements keyboard-reachable
+- Visible focus rings (2 px brand ring)
+- 4.5:1 contrast minimum (already met by brand colors)
+- `aria-label` on icon buttons, `role="alert"` on toasts
+- Respects `prefers-reduced-motion` (Motion handles this automatically)
+
+## Implementation Phases (Vertical Slices)
+
+Each phase is a shippable PR that keeps the app runnable. The legacy `renderer.js` is gradually replaced; until each phase is complete, the old renderer code still runs the missing parts.
+
+| # | Phase | Output | Acceptance |
+|---|---|---|---|
+| 1 | **Foundation** | shadcn installed; `next-themes`, `motion`, `react-hook-form`, `zod`, `@dnd-kit/core`, `react-resizable-panels`, `sonner` installed; design tokens finalized; `lib/utils.ts` (`cn`), `lib/ipc.ts` typed wrappers, `lib/motion.ts` preset transitions, `App.tsx` shell skeleton renders | `npm run build` succeeds; dev server shows the new shell with theme toggle working |
+| 2 | **App shell + layout** | `AppHeader`, `TabBar`, `Toolbar`, `Breadcrumb`, `StatusBar`, `ResizablePaneGroup` with sidebar toggle and draggable divider. Empty editor/preview panes. | Resize divider with mouse and arrow keys; sidebar collapses; pane sizes persist. |
+| 3 | **Editor pane** | CodeMirror 6 wrapped, dark/light themes wired to shadcn theme, syntax highlighting, line numbers, search, autocomplete | Open `.md` file → renders in editor; can edit and save. |
+| 4 | **Preview pane** | marked + DOMPurify + KaTeX + Mermaid + highlight.js. Bidirectional scroll sync with editor. | Open file → preview renders, follows cursor. |
+| 5 | **File tree + tabs** | Sidebar file tree (read directory on demand, lazy-expand children only on click). Tabs for open files. Dirty state indicator. File content is read from disk only when the tab is activated. | Open folder → root populates; click folder → children load; click file → opens in tab; close tab reverts dirty. |
+| 6 | **Native menus + toolbar** | Replace the legacy `CommandPalette` with full menus (File / Edit / View / Insert / Format / Tools / Help) bound to keyboard shortcuts. Toolbar buttons. | All menu items invoke the right action; shortcuts work; toolbar reflects active state. |
+| 7 | **Modals** | Export dialog (PDF/DOCX/HTML/batch), Settings side-sheet (Editor/Theme/Export/Plugins/About tabs), About dialog, Confirm-destructive dialog | All dialogs and sheet render with proper motion; settings persist; export works end-to-end. |
+| 8 | **Toasts** | Sonner wired into all async operations (save, export, errors, tool missing) | All operations give appropriate feedback; no silent failures. |
+| 9 | **Advanced tools** | Zen mode (full-viewport toggle), REPL (bottom-pinned panel), ASCII generator, Table generator, Word export template picker, Print preview | Each tool is feature-complete vs. legacy version. |
+| 10 | **Polish + delete legacy** | Visual regression snapshots locked; remove `renderer.js` and old `styles*.css` references from build; `npm run build:linux` produces a working installer | Final PR ships an installer with no legacy code paths. |
+
+## Risks and Mitigations
+
+| Risk | Mitigation |
+|---|---|
+| shadcn CLI requires Vite (not vanilla Electron renderer) | Vite is already configured for the renderer in `vite.renderer.config.ts`; the CLI works against the same project. |
+| shadcn CLI assumes Tailwind is at project root; we have it in renderer/ only | Point the CLI at `src/renderer/components.json` and set `tailwind.css` to the right path. |
+| Marked + KaTeX + Mermaid + highlight.js together is heavy | Lazy-load Mermaid (only when `mermaid` code block encountered). KaTeX is loaded once, cached. |
+| Editor content state can be megabytes → re-render storms | Editor content lives in its own slice; preview subscribes to a derived/cached HTML string; components use `useShallow` / selector subscriptions. |
+| Bidirectional scroll sync loops | `useEffect` debounce + ignore if cursor/selection is the sync source. |
+| CodeMirror 6 doesn't ship a Tailwind theme by default | Use `@codemirror/theme-one-dark` for dark; build a custom theme that pulls from CSS variables for light. |
+| The legacy `renderer.js` and `styles*.css` are referenced from `index.html` (now `src/renderer/index.html`) | Phase 10 deletes the references; until then, both run side-by-side and the new React app sits in a known root div. |
+| Electron `nodeIntegration` is off; we use contextBridge | Already the case. Document the contract clearly in `lib/ipc.ts`. |
+
+## Open Questions (to confirm before implementation)
+
+None. All major decisions are locked. Defaults will be used unless the user overrides them when reviewing the implementation plan.
+
+## References
+
+- `src/renderer.js` (213 KB) — legacy renderer being replaced
+- `src/styles.css` (74 KB), `src/styles-modern.css` (71 KB), `src/styles-concreteinfo.css` (21 KB) — legacy styles being replaced
+- `src/renderer/styles/globals.css` — already shadcn-compatible (HSL CSS variables)
+- `src/renderer/App.tsx` — empty skeleton that references components we will build
+- `tailwind.config.js` — brand colors and fonts already defined
+- `vite.renderer.config.ts` — Vite + React plugin already configured
+- `package.json` — CodeMirror 6, TanStack Table, lucide-react, cva, clsx, tailwind-merge, tailwindcss-animate already installed

package.json

@@ -1,6 +1,6 @@
 {
   "name": "markdown-converter",
-  "version": "4.4.3",
+  "version": "4.4.2",
   "description": "Professional Markdown editor and universal file converter with PDF editing, batch processing, and syntax highlighting",
   "main": "src/main.js",
   "scripts": {
@@ -8,6 +8,9 @@
     "test": "jest",
     "test:watch": "jest --watch",
     "test:coverage": "jest --coverage",
+    "test:renderer": "vitest run",
+    "test:renderer:watch": "vitest",
+    "test:renderer:coverage": "vitest run --coverage",
     "lint": "eslint src tests",
     "lint:fix": "eslint src tests --fix",
     "format": "prettier --write src tests",
@@ -43,7 +46,19 @@
     "url": "https://github.com/amitwh/markdown-converter"
   },
   "devDependencies": {
+    "@playwright/test": "^1.60.0",
     "@testing-library/dom": "^10.4.1",
+    "@testing-library/jest-dom": "^6.9.1",
+    "@testing-library/react": "^16.3.2",
+    "@testing-library/user-event": "^14.6.1",
+    "@types/node": "^25.9.1",
+    "@types/react": "^19.2.16",
+    "@types/react-dom": "^19.2.3",
+    "@vitejs/plugin-react": "^6.0.2",
+    "@vitest/ui": "^4.1.8",
+    "autoprefixer": "^10.5.0",
+    "class-variance-authority": "^0.7.1",
+    "clsx": "^2.1.1",
     "cross-env": "^10.0.0",
     "electron": "^41.1.1",
     "electron-builder": "^26.0.12",
@@ -52,8 +67,17 @@
     "eslint-plugin-prettier": "^5.5.4",
     "jest": "^30.2.0",
     "jest-environment-jsdom": "^30.2.0",
+    "jsdom": "^29.1.1",
+    "lucide-react": "^1.17.0",
+    "postcss": "^8.5.15",
     "prettier": "^3.7.4",
-    "sharp": "^0.34.3"
+    "sharp": "^0.34.3",
+    "tailwind-merge": "^3.6.0",
+    "tailwindcss": "^3.4.19",
+    "tailwindcss-animate": "^1.0.7",
+    "typescript": "^6.0.3",
+    "vite": "^8.0.16",
+    "vitest": "^4.1.8"
   },
   "dependencies": {
     "@codemirror/autocomplete": "^6.20.1",
@@ -70,6 +94,12 @@
     "@codemirror/state": "^6.5.4",
     "@codemirror/theme-one-dark": "^6.1.3",
     "@codemirror/view": "^6.39.16",
+    "@dnd-kit/core": "^6.3.1",
+    "@dnd-kit/sortable": "^10.0.0",
+    "@dnd-kit/utilities": "^3.2.2",
+    "@hookform/resolvers": "^5.4.0",
+    "@radix-ui/react-slot": "^1.2.4",
+    "@tanstack/react-table": "^8.21.3",
     "codemirror": "^6.0.2",
     "core-util-is": "^1.0.3",
     "docx": "^9.6.0",
@@ -79,16 +109,26 @@
     "ffmpeg-static": "^5.3.0",
     "highlight.js": "^11.11.1",
     "html2pdf.js": "^0.14.0",
+    "immer": "^11.1.8",
     "marked": "^17.0.3",
     "marked-footnote": "^1.4.0",
     "marked-highlight": "^2.2.3",
     "mermaid": "^11.12.3",
+    "motion": "^12.40.0",
+    "next-themes": "^0.4.6",
     "pdf-lib": "^1.17.1",
     "pdfjs-dist": "^5.5.207",
     "pdfkit": "^0.17.2",
     "pizzip": "^3.2.0",
+    "react": "^19.2.7",
+    "react-dom": "^19.2.7",
+    "react-hook-form": "^7.77.0",
+    "react-resizable-panels": "^4.11.2",
     "simple-git": "^3.32.3",
-    "tslib": "^2.8.1"
+    "sonner": "^2.0.7",
+    "tslib": "^2.8.1",
+    "zod": "^4.4.3",
+    "zustand": "^5.0.14"
   },
   "overrides": {
     "jszip": "^3.10.1",

postcss.config.js

@@ -0,0 +1,6 @@
+module.exports = {
+  plugins: {
+    tailwindcss: {},
+    autoprefixer: {},
+  },
+}

src/index.html

@@ -4,7 +4,7 @@
     <meta charset="UTF-8">
     <!-- CSP: unsafe-inline/unsafe-eval required for marked.js extensions and Mermaid -->
     <!-- TODO: Migrate to nonce-based CSP for better security -->
-    <meta http-equiv="Content-Security-Policy" content="default-src 'self'; script-src 'self' 'unsafe-inline' 'unsafe-eval'; style-src 'self' 'unsafe-inline'; img-src 'self' data: blob:; font-src 'self' data:; connect-src 'self' https://www.plantuml.com;">
+    <meta http-equiv="Content-Security-Policy" content="default-src 'self'; script-src 'self' 'unsafe-inline' 'unsafe-eval' https://cdn.jsdelivr.net; style-src 'self' 'unsafe-inline' https://cdn.jsdelivr.net; img-src 'self' data: blob:; font-src 'self' data: https://cdn.jsdelivr.net; connect-src 'self' https://www.plantuml.com;">
     <meta name="viewport" content="width=device-width, initial-scale=1.0">
     <title>MarkdownConverter</title>
     <!-- Design tokens - loaded first for CSS variable availability -->

src/main.js

@@ -242,7 +242,9 @@ function runPandoc(args, callback) {
 function runPandocCmd(cmdString, callback) {
   const parsed = parseCommand(cmdString);
   // Skip 'pandoc' if it's the first element (command itself)
-  const args = parsed.command === 'pandoc' ? parsed.args : [parsed.command, ...parsed.args];
+  // Use path.basename to handle full paths like bin/linux/pandoc
+  const cmdBase = path.basename(parsed.command).replace(/\.exe$/i, '');
+  const args = cmdBase === 'pandoc' ? parsed.args : [parsed.command, ...parsed.args];
   const pandocPath = getPandocPath();
   execFile(pandocPath, args, { maxBuffer: 10 * 1024 * 1024 }, callback);
 }

src/renderer.js

@@ -1,9 +1,20 @@
 /**
  * MarkdownConverter Renderer Process
- * @version 4.4.3
+ * @version 4.4.2
  */
 
 const { ipcRenderer } = require('electron');
+
+// Shim window.electronAPI for main window which uses nodeIntegration
+// without preload script (window.electronAPI is normally set by preload.js).
+if (typeof window !== 'undefined' && !window.electronAPI) {
+    window.electronAPI = {
+        getAppVersion: () => ipcRenderer.invoke('get-app-version'),
+        invoke: (channel, data) => ipcRenderer.invoke(channel, data),
+        on: (channel, callback) => ipcRenderer.on(channel, (event, ...args) => callback(...args))
+    };
+}
+
 const marked = require('marked');
 const { markedHighlight } = require('marked-highlight');
 const createDOMPurify = require('dompurify');
@@ -11,53 +22,12 @@ const DOMPurify = createDOMPurify(window);
 const hljs = require('highlight.js');
 const { createEditor } = require('./editor/codemirror-setup');
 const { undo, redo } = require('@codemirror/commands');
-
-// Define a fallback window.electronAPI object for when contextIsolation is disabled
-// and the preload script is not loaded in the main window context.
-if (typeof window !== 'undefined' && !window.electronAPI) {
-    window.electronAPI = {
-        send: (channel, data) => {
-            ipcRenderer.send(channel, data);
-        },
-        invoke: async (channel, data) => {
-            return await ipcRenderer.invoke(channel, data);
-        },
-        on: (channel, callback) => {
-            const subscription = (event, ...args) => callback(...args);
-            ipcRenderer.on(channel, subscription);
-            return () => {
-                ipcRenderer.removeListener(channel, subscription);
-            };
-        },
-        once: (channel, callback) => {
-            ipcRenderer.once(channel, (event, ...args) => callback(...args));
-        },
-        removeAllListeners: (channel) => {
-            ipcRenderer.removeAllListeners(channel);
-        },
-        getAppVersion: () => ipcRenderer.invoke('get-app-version'),
-        file: {
-            read: (filePath) => ipcRenderer.invoke('read-file', filePath),
-            write: (filePath, content) => ipcRenderer.invoke('write-file', { path: filePath, content }),
-            delete: (filePath) => ipcRenderer.invoke('delete-file', filePath),
-            ensureDir: (dirPath) => ipcRenderer.invoke('ensure-directory', dirPath),
-            exists: (filePath) => ipcRenderer.invoke('path-exists', filePath),
-            isDirectory: (filePath) => ipcRenderer.invoke('is-directory', filePath),
-            copy: (source, destination) => ipcRenderer.invoke('copy-path', { source, destination }),
-            move: (source, destination) => ipcRenderer.invoke('move-path', { source, destination })
-        }
-    };
-}
-
-// Use window.ModalManager if already set by script tag, otherwise require it.
-// This prevents "Identifier 'ModalManager' has already been declared" when
-// both the script tag in index.html and CommonJS require() declare it.
-let _ModalManager;
-if (typeof window !== 'undefined' && window.ModalManager) {
-    _ModalManager = window.ModalManager;
-} else {
+// ModalManager is loaded via <script src="utils/ModalManager.js"> in index.html.
+// It already exists in the global scope — re-declaring with let/const causes
+// SyntaxError: "Identifier 'ModalManager' has already been declared".
+if (typeof ModalManager === 'undefined') {
     const result = require('./utils/ModalManager');
-    _ModalManager = result.ModalManager || result;
+    ModalManager = result.ModalManager || result;
 }
 // Lazy-loaded modules — defer heavy imports until first use
 let _SidebarManager, _renderTemplatesPanel, _renderExplorerPanel, _renderGitPanel, _renderSnippetsPanel;
@@ -520,38 +490,7 @@ class TabManager {
         document.querySelector('.editor-container').appendChild(tabContent);
 
         // Initialize CodeMirror editor
-        const editorContainer = document.getElementById(`editor-cm-${tab.id}`);
-        if (editorContainer) {
-            const isDark = document.body.className.includes('dark');
-            tab.editorView = createEditor(editorContainer, {
-                content: tab.content,
-                onChange: (newContent) => {
-                    tab.content = newContent;
-                    tab.isDirty = true;
-                    // Dynamically enable/disable Large File Mode on edit
-                    if (newContent.length > 1024 * 1024) {
-                        if (!tab.largeFileMode) {
-                            tab.largeFileMode = true;
-                            this.isPreviewVisible = false;
-                            this.updatePreviewVisibility();
-                            notifyUser('Large content detected (>1MB). Large File Mode enabled to maintain peak responsiveness. Live preview auto-render is disabled.', 'warning');
-                        }
-                    } else {
-                        tab.largeFileMode = false;
-                    }
-                    this.updatePreview(tab.id);
-                    this.updateWordCount();
-                    this.updateTabBar();
-                    if (outlinePanelContainer?._refreshOutline) outlinePanelContainer._refreshOutline();
-                },
-                onUpdate: (view) => {
-                    this.updateCursorPosition(view);
-                    if (outlinePanelContainer?._setActiveHeading) outlinePanelContainer._setActiveHeading(view.state.doc.lineAt(view.state.selection.main.head).number);
-                },
-                isDark,
-                showLineNumbers: this.showLineNumbers,
-            });
-        }
+        this.ensureEditor(tab);
     }
     
     switchToTab(tabId) {
@@ -1522,9 +1461,47 @@ class TabManager {
         return tab?.content || '';
     }
 
+    // Ensure a tab has a CodeMirror editor (lazy creation fallback)
+    ensureEditor(tab) {
+        if (tab.editorView) return true;
+        const editorContainer = document.getElementById(`editor-cm-${tab.id}`);
+        if (!editorContainer) {
+            console.error(`[ensureEditor] editor-cm-${tab.id} not found in DOM`);
+            return false;
+        }
+        try {
+            const isDark = document.body.className.includes('dark');
+            tab.editorView = createEditor(editorContainer, {
+                content: tab.content,
+                onChange: (newContent) => {
+                    tab.content = newContent;
+                    tab.isDirty = true;
+                    this.updatePreview(tab.id);
+                    this.updateWordCount();
+                    this.updateTabBar();
+                    if (outlinePanelContainer?._refreshOutline) outlinePanelContainer._refreshOutline();
+                },
+                onUpdate: (view) => {
+                    this.updateCursorPosition(view);
+                    if (outlinePanelContainer?._setActiveHeading) outlinePanelContainer._setActiveHeading(view.state.doc.lineAt(view.state.selection.main.head).number);
+                },
+                isDark,
+                showLineNumbers: this.showLineNumbers,
+            });
+            console.log(`[ensureEditor] Created editor for tab ${tab.id}`);
+            return true;
+        } catch (err) {
+            console.error(`[ensureEditor] Failed to create editor for tab ${tab.id}:`, err);
+            return false;
+        }
+    }
+
     // Set content in editor
     setEditorContent(tabId, content) {
         const tab = this.tabs.get(tabId);
+        if (!tab?.editorView) {
+            this.ensureEditor(tab);
+        }
         if (tab?.editorView) {
             tab.editorView.dispatch({
                 changes: { from: 0, to: tab.editorView.state.doc.length, insert: content }
@@ -1581,7 +1558,6 @@ let tabManager;
 let replPanel;
 
 document.addEventListener('DOMContentLoaded', async () => {
-    const ModalManager = _ModalManager;
     tabManager = new TabManager();
 
     // Load saved Custom Preview CSS if present
@@ -1714,11 +1690,6 @@ document.addEventListener('DOMContentLoaded', async () => {
     });
 
     const statusBarRight = document.querySelector('.status-bar-right');
-
-    // Initialize command palette
-    const CommandPalette = getCommandPalette();
-    const commandPalette = new CommandPalette();
-
     const pluginRegistry = new PluginRegistry({
         sidebar: sidebarManager,
         commands: commandPalette,
@@ -1774,7 +1745,8 @@ document.addEventListener('DOMContentLoaded', async () => {
         const welcomeHtml = getCreateWelcomeContent()(recentFiles, appVersion);
 
         const tab = tabManager.tabs.get(tabManager.activeTabId);
-        if (tab) {
+        // Only show welcome if no file was opened while we were awaiting
+        if (tab && !tab.filePath && tab.content === '') {
             tab.title = 'Welcome';
             tab.content = '';
             const preview = document.getElementById(`preview-${tab.id}`);
@@ -1855,6 +1827,10 @@ document.addEventListener('DOMContentLoaded', async () => {
         }
     });
 
+    // Initialize command palette
+    const CommandPalette = getCommandPalette();
+    const commandPalette = new CommandPalette();
+
     // Initialize print preview
     const PrintPreview = getPrintPreview();
     const printPreview = new PrintPreview();
@@ -1939,27 +1915,9 @@ document.addEventListener('DOMContentLoaded', async () => {
     });
 
     // Initialize CodeMirror for the initial tab (tab 1)
-    const initialEditorContainer = document.getElementById('editor-cm-1');
-    if (initialEditorContainer) {
-        const tab = tabManager.tabs.get(1);
-        const isDark = document.body.className.includes('dark');
-        tab.editorView = createEditor(initialEditorContainer, {
-            content: tab.content,
-            onChange: (newContent) => {
-                tab.content = newContent;
-                tab.isDirty = true;
-                tabManager.updatePreview(tab.id);
-                tabManager.updateWordCount();
-                tabManager.updateTabBar();
-                if (outlinePanelContainer?._refreshOutline) outlinePanelContainer._refreshOutline();
-            },
-            onUpdate: (view) => {
-                tabManager.updateCursorPosition(view);
-                if (outlinePanelContainer?._setActiveHeading) outlinePanelContainer._setActiveHeading(view.state.doc.lineAt(view.state.selection.main.head).number);
-            },
-            isDark,
-            showLineNumbers: tabManager.showLineNumbers,
-        });
+    const initialTab = tabManager.tabs.get(1);
+    if (initialTab) {
+        tabManager.ensureEditor(initialTab);
     }
 
     // Request current theme

src/renderer/App.tsx

@@ -0,0 +1,7 @@
+import { AppShell } from './components/layout/AppShell';
+
+function App() {
+  return <AppShell />;
+}
+
+export default App;

src/renderer/components/layout/AppHeader.tsx

@@ -0,0 +1,41 @@
+import { PanelLeft, PanelRight } from 'lucide-react';
+import { Button } from '@/components/ui/button';
+import { ThemeToggle } from '@/components/theme-toggle';
+import { useAppStore } from '@/stores/app-store';
+
+export function AppHeader() {
+  const { sidebarVisible, previewVisible, toggleSidebar, togglePreview } = useAppStore();
+
+  return (
+    <header className="flex h-14 items-center justify-between border-b border-border bg-card/40 px-4 backdrop-blur">
+      <div className="flex items-center gap-3">
+        <div
+          className="h-7 w-7 rounded-md bg-gradient-to-br from-brand to-brand-dark shadow-[var(--shadow-glow-brand)]"
+          aria-label="MarkdownConverter logo"
+        />
+        <h1 className="font-display text-lg font-bold tracking-tight">MarkdownConverter</h1>
+      </div>
+      <div className="flex items-center gap-1">
+        <Button
+          variant="ghost"
+          size="icon"
+          aria-label="Toggle sidebar"
+          aria-pressed={sidebarVisible}
+          onClick={toggleSidebar}
+        >
+          <PanelLeft className="h-4 w-4" />
+        </Button>
+        <Button
+          variant="ghost"
+          size="icon"
+          aria-label="Toggle preview"
+          aria-pressed={previewVisible}
+          onClick={togglePreview}
+        >
+          <PanelRight className="h-4 w-4" />
+        </Button>
+        <ThemeToggle />
+      </div>
+    </header>
+  );
+}

src/renderer/components/layout/AppShell.tsx

@@ -0,0 +1,53 @@
+import { AppHeader } from './AppHeader';
+import { TabBar } from './TabBar';
+import { Toolbar } from './Toolbar';
+import { Breadcrumb } from './Breadcrumb';
+import { StatusBar } from './StatusBar';
+import { useAppStore } from '@/stores/app-store';
+import { ResizablePanelGroup, ResizablePanel, ResizableHandle } from '@/components/ui/resizable';
+
+export function AppShell() {
+  const { sidebarVisible, previewVisible, paneSizes, setPaneSizes } = useAppStore();
+
+  return (
+    <div className="flex h-screen flex-col bg-background text-foreground">
+      <AppHeader />
+      <TabBar />
+      <Toolbar />
+      <Breadcrumb />
+      <main className="flex-1 overflow-hidden">
+        <ResizablePanelGroup
+          direction="horizontal"
+          onLayout={(sizes) => setPaneSizes({ sidebar: sizes[0], editor: sizes[1], preview: sizes[2] })}
+        >
+          {sidebarVisible && (
+            <>
+              <ResizablePanel defaultSize={paneSizes.sidebar} minSize={15} maxSize={40}>
+                <aside className="h-full border-r border-border bg-card/10 p-3 text-sm text-muted-foreground">
+                  File tree placeholder
+                </aside>
+              </ResizablePanel>
+              <ResizableHandle />
+            </>
+          )}
+          <ResizablePanel defaultSize={previewVisible ? paneSizes.editor : 100} minSize={20}>
+            <section className="h-full bg-background p-4 text-sm text-muted-foreground">
+              Editor placeholder
+            </section>
+          </ResizablePanel>
+          {previewVisible && (
+            <>
+              <ResizableHandle />
+              <ResizablePanel defaultSize={paneSizes.preview} minSize={20}>
+                <section className="h-full border-l border-border bg-card/10 p-4 text-sm text-muted-foreground">
+                  Preview placeholder
+                </section>
+              </ResizablePanel>
+            </>
+          )}
+        </ResizablePanelGroup>
+      </main>
+      <StatusBar />
+    </div>
+  );
+}

src/renderer/components/layout/Breadcrumb.tsx

@@ -0,0 +1,7 @@
+export function Breadcrumb() {
+  return (
+    <nav aria-label="File path" className="flex h-7 items-center border-b border-border bg-card/10 px-3 text-xs text-muted-foreground">
+      <span>No file selected</span>
+    </nav>
+  );
+}

src/renderer/components/layout/StatusBar.tsx

@@ -0,0 +1,14 @@
+export function StatusBar() {
+  return (
+    <footer className="flex h-7 items-center justify-between border-t border-border bg-card/20 px-3 text-xs text-muted-foreground">
+      <div className="flex items-center gap-4">
+        <span>0 words</span>
+        <span>UTF-8</span>
+      </div>
+      <div className="flex items-center gap-4">
+        <span>Ln 1, Col 1</span>
+        <span>Markdown</span>
+      </div>
+    </footer>
+  );
+}

src/renderer/components/layout/TabBar.tsx

@@ -0,0 +1,7 @@
+export function TabBar() {
+  return (
+    <div className="flex h-9 items-center border-b border-border bg-card/20 px-3 text-xs text-muted-foreground">
+      <span>No files open</span>
+    </div>
+  );
+}

src/renderer/components/layout/Toolbar.tsx

@@ -0,0 +1,15 @@
+import { Bold, Italic, List, ListOrdered, Code, Link as LinkIcon } from 'lucide-react';
+import { Button } from '@/components/ui/button';
+
+export function Toolbar() {
+  return (
+    <div className="flex h-10 items-center gap-1 border-b border-border bg-card/10 px-3">
+      <Button variant="ghost" size="icon" aria-label="Bold"><Bold className="h-4 w-4" /></Button>
+      <Button variant="ghost" size="icon" aria-label="Italic"><Italic className="h-4 w-4" /></Button>
+      <Button variant="ghost" size="icon" aria-label="Unordered list"><List className="h-4 w-4" /></Button>
+      <Button variant="ghost" size="icon" aria-label="Ordered list"><ListOrdered className="h-4 w-4" /></Button>
+      <Button variant="ghost" size="icon" aria-label="Code"><Code className="h-4 w-4" /></Button>
+      <Button variant="ghost" size="icon" aria-label="Link"><LinkIcon className="h-4 w-4" /></Button>
+    </div>
+  );
+}

src/renderer/components/theme-provider.tsx

@@ -0,0 +1,6 @@
+import { ThemeProvider as NextThemesProvider } from 'next-themes';
+import type { ComponentProps } from 'react';
+
+export function ThemeProvider({ children, ...props }: ComponentProps<typeof NextThemesProvider>) {
+  return <NextThemesProvider {...props}>{children}</NextThemesProvider>;
+}

src/renderer/components/theme-toggle.tsx

@@ -0,0 +1,30 @@
+import { useTheme } from 'next-themes';
+import { Moon, Sun } from 'lucide-react';
+import { Button } from '@/components/ui/button';
+import { useEffect, useState } from 'react';
+
+export function ThemeToggle() {
+  const { resolvedTheme, setTheme } = useTheme();
+  const [mounted, setMounted] = useState(false);
+  useEffect(() => setMounted(true), []);
+
+  if (!mounted) {
+    return (
+      <Button variant="ghost" size="icon" aria-label="Toggle theme" className="opacity-0">
+        <Sun className="h-4 w-4" />
+      </Button>
+    );
+  }
+
+  const isDark = resolvedTheme === 'dark';
+  return (
+    <Button
+      variant="ghost"
+      size="icon"
+      aria-label="Toggle theme"
+      onClick={() => setTheme(isDark ? 'light' : 'dark')}
+    >
+      {isDark ? <Sun className="h-4 w-4" /> : <Moon className="h-4 w-4" />}
+    </Button>
+  );
+}

src/renderer/components/ui/button.tsx

@@ -0,0 +1,57 @@
+import * as React from "react"
+import { Slot } from "@radix-ui/react-slot"
+import { cva, type VariantProps } from "class-variance-authority"
+
+import { cn } from "@/lib/utils"
+
+const buttonVariants = cva(
+  "inline-flex items-center justify-center gap-2 whitespace-nowrap rounded-md text-sm font-medium transition-colors focus-visible:outline-none focus-visible:ring-1 focus-visible:ring-ring disabled:pointer-events-none disabled:opacity-50 [&_svg]:pointer-events-none [&_svg]:size-4 [&_svg]:shrink-0",
+  {
+    variants: {
+      variant: {
+        default:
+          "bg-primary text-primary-foreground shadow hover:bg-primary/90",
+        destructive:
+          "bg-destructive text-destructive-foreground shadow-sm hover:bg-destructive/90",
+        outline:
+          "border border-input bg-background shadow-sm hover:bg-accent hover:text-accent-foreground",
+        secondary:
+          "bg-secondary text-secondary-foreground shadow-sm hover:bg-secondary/80",
+        ghost: "hover:bg-accent hover:text-accent-foreground",
+        link: "text-primary underline-offset-4 hover:underline",
+      },
+      size: {
+        default: "h-9 px-4 py-2",
+        sm: "h-8 rounded-md px-3 text-xs",
+        lg: "h-10 rounded-md px-8",
+        icon: "h-9 w-9",
+      },
+    },
+    defaultVariants: {
+      variant: "default",
+      size: "default",
+    },
+  }
+)
+
+export interface ButtonProps
+  extends React.ButtonHTMLAttributes<HTMLButtonElement>,
+    VariantProps<typeof buttonVariants> {
+  asChild?: boolean
+}
+
+const Button = React.forwardRef<HTMLButtonElement, ButtonProps>(
+  ({ className, variant, size, asChild = false, ...props }, ref) => {
+    const Comp = asChild ? Slot : "button"
+    return (
+      <Comp
+        className={cn(buttonVariants({ variant, size, className }))}
+        ref={ref}
+        {...props}
+      />
+    )
+  }
+)
+Button.displayName = "Button"
+
+export { Button, buttonVariants }

src/renderer/components/ui/resizable.tsx

@@ -0,0 +1,62 @@
+"use client"
+
+import * as React from "react"
+import { GripVertical } from "lucide-react"
+import * as ResizablePrimitive from "react-resizable-panels"
+
+import { cn } from "@/lib/utils"
+
+const ResizablePanelGroup = React.forwardRef<
+  React.ElementRef<typeof ResizablePrimitive.Group>,
+  React.ComponentPropsWithoutRef<typeof ResizablePrimitive.Group>
+>(({ className, ...props }, ref) => (
+  <ResizablePrimitive.Group
+    ref={ref}
+    className={cn(
+      "flex h-full w-full data-[panel-group-direction=vertical]:flex-col",
+      className
+    )}
+    {...props}
+  />
+))
+ResizablePanelGroup.displayName = "ResizablePanelGroup"
+
+const ResizablePanel = React.forwardRef<
+  React.ElementRef<typeof ResizablePrimitive.Panel>,
+  React.ComponentPropsWithoutRef<typeof ResizablePrimitive.Panel>
+>(({ className, ...props }, ref) => (
+  <ResizablePrimitive.Panel
+    ref={ref}
+    className={cn(
+      "h-full w-full overflow-hidden",
+      className
+    )}
+    {...props}
+  />
+))
+ResizablePanel.displayName = "ResizablePanel"
+
+const ResizableHandle = ({
+  withHandle,
+  className,
+  ...props
+}: React.ComponentPropsWithoutRef<typeof ResizablePrimitive.Separator> & {
+  withHandle?: boolean
+}) => (
+  <ResizablePrimitive.Separator
+    className={cn(
+      "relative flex w-px items-center justify-center bg-border after:absolute after:inset-y-0 after:left-1/2 after:w-1 after:-translate-x-1/2 focus-visible:outline-none focus-visible:ring-1 focus-visible:ring-ring focus-visible:ring-offset-1 data-[panel-group-direction=vertical]:h-px data-[panel-group-direction=vertical]:w-full data-[panel-group-direction=vertical]:after:left-0 data-[panel-group-direction=vertical]:after:h-1 data-[panel-group-direction=vertical]:after:w-full data-[panel-group-direction=vertical]:after:-translate-y-1/2 data-[panel-group-direction=vertical]:after:translate-x-0 [&[data-panel-group-direction=vertical]>div]:rotate-90",
+      className
+    )}
+    {...props}
+  >
+    {withHandle && (
+      <div className="z-10 flex h-4 w-3 items-center justify-center rounded-sm border bg-border">
+        <GripVertical className="h-2.5 w-2.5" />
+      </div>
+    )}
+  </ResizablePrimitive.Separator>
+)
+ResizableHandle.displayName = "ResizableHandle"
+
+export { ResizablePanelGroup, ResizablePanel, ResizableHandle }

src/renderer/index.html

@@ -0,0 +1,16 @@
+<!DOCTYPE html>
+<html lang="en">
+<head>
+  <meta charset="UTF-8">
+  <meta http-equiv="Content-Security-Policy" content="default-src 'self'; script-src 'self' 'unsafe-inline' 'unsafe-eval'; style-src 'self' 'unsafe-inline'; img-src 'self' data: blob:; font-src 'self' data:; connect-src 'self';">
+  <meta name="viewport" content="width=device-width, initial-scale=1.0">
+  <title>MarkdownConverter</title>
+  <link rel="preconnect" href="https://fonts.googleapis.com">
+  <link rel="preconnect" href="https://fonts.gstatic.com" crossorigin>
+  <link href="https://fonts.googleapis.com/css2?family=Plus+Jakarta+Sans:wght@400;500;600;700;800&family=JetBrains+Mono:wght@400;500;600;700&display=swap" rel="stylesheet">
+</head>
+<body class="font-sans antialiased">
+  <div id="root"></div>
+  <script type="module" src="./main.tsx"></script>
+</body>
+</html>

src/renderer/lib/ipc.ts

@@ -0,0 +1,94 @@
+import type {
+  IpcResult,
+  FileResult,
+  FileEntry,
+  PdfOptions,
+  DocxOptions,
+  HtmlOptions,
+  ExportResult,
+  BatchItem,
+  BatchOptions,
+  BatchResult,
+} from '@/types/ipc';
+
+type ChannelMissing = { code: 'CHANNEL_MISSING'; message: string };
+
+function wrap<T>(fn: () => Promise<T>): Promise<IpcResult<T | ChannelMissing>> {
+  if (typeof window === 'undefined' || !window.electronAPI) {
+    return Promise.resolve({
+      ok: false,
+      error: { code: 'NO_BRIDGE', message: 'window.electronAPI is unavailable' },
+    });
+  }
+  return fn().then(
+    (data) => ({ ok: true as const, data }),
+    (err: Error) => ({
+      ok: false as const,
+      error: { code: err.name || 'IPC_ERROR', message: err.message || String(err) },
+    }),
+  );
+}
+
+function safeCall<T extends (...args: any[]) => Promise<any>>(
+  channel: string,
+  method: string,
+  ...args: Parameters<T>
+): Promise<IpcResult<Awaited<ReturnType<T>> | ChannelMissing>> {
+  if (typeof window === 'undefined' || !window.electronAPI) {
+    return Promise.resolve({
+      ok: false,
+      error: { code: 'NO_BRIDGE', message: 'window.electronAPI is unavailable' },
+    });
+  }
+  const target = (window.electronAPI as any)[channel]?.[method];
+  if (!target) {
+    return Promise.resolve({
+      ok: false,
+      error: { code: 'CHANNEL_MISSING', message: `Missing channel: ${channel}.${method}` },
+    });
+  }
+  if (typeof target !== 'function') {
+    return Promise.resolve({
+      ok: false,
+      error: { code: 'CHANNEL_MISSING', message: `Not a function: ${channel}.${method}` },
+    });
+  }
+  return wrap(() => target(...args));
+}
+
+export const ipc = {
+  file: {
+    open: (): Promise<IpcResult<FileResult | ChannelMissing>> =>
+      safeCall('file', 'open'),
+    read: (path: string): Promise<IpcResult<string | ChannelMissing>> =>
+      safeCall('file', 'read', path),
+    write: (path: string, content: string): Promise<IpcResult<void | ChannelMissing>> =>
+      safeCall('file', 'write', path, content),
+    list: (dir: string): Promise<IpcResult<FileEntry[] | ChannelMissing>> =>
+      safeCall('file', 'list', dir),
+    onChange: (cb: (path: string) => void): (() => void) => {
+      if (typeof window === 'undefined' || !window.electronAPI?.file?.onChange) {
+        return () => {};
+      }
+      return window.electronAPI.file.onChange(cb);
+    },
+  },
+  export: {
+    pdf: (opts: PdfOptions): Promise<IpcResult<ExportResult | ChannelMissing>> =>
+      safeCall('export', 'pdf', opts),
+    docx: (opts: DocxOptions): Promise<IpcResult<ExportResult | ChannelMissing>> =>
+      safeCall('export', 'docx', opts),
+    html: (opts: HtmlOptions): Promise<IpcResult<ExportResult | ChannelMissing>> =>
+      safeCall('export', 'html', opts),
+    batch: (items: BatchItem[], opts: BatchOptions): Promise<IpcResult<BatchResult | ChannelMissing>> =>
+      safeCall('export', 'batch', items, opts),
+  },
+  app: {
+    getVersion: (): Promise<IpcResult<string | ChannelMissing>> =>
+      safeCall('app', 'getVersion'),
+    openExternal: (url: string): Promise<IpcResult<void | ChannelMissing>> =>
+      safeCall('app', 'openExternal', url),
+    showItemInFolder: (path: string): Promise<IpcResult<void | ChannelMissing>> =>
+      safeCall('app', 'showItemInFolder', path),
+  },
+};

src/renderer/lib/motion.ts

@@ -0,0 +1,41 @@
+import type { Transition, Variants } from 'motion/react';
+
+export const fadeIn: Transition = {
+  duration: 0.2,
+  ease: 'easeOut',
+};
+
+export const slideInRight: Variants = {
+  x: '100%',
+  initial: { x: '100%', opacity: 0 },
+  animate: { x: 0, opacity: 1, transition: { duration: 0.3, ease: [0.16, 1, 0.3, 1] } },
+  exit: { x: '100%', opacity: 0, transition: { duration: 0.2, ease: 'easeIn' } },
+};
+
+export const modalPop: Variants = {
+  scale: 0.96,
+  opacity: 0,
+  initial: { scale: 0.96, opacity: 0 },
+  animate: { scale: 1, opacity: 1, transition: { duration: 0.2, ease: 'easeOut' } },
+  exit: { scale: 0.96, opacity: 0, transition: { duration: 0.15, ease: 'easeIn' } },
+};
+
+export const toastSpring: Transition = {
+  type: 'spring',
+  stiffness: 300,
+  damping: 30,
+};
+
+export const sidebarToggle: Transition = {
+  duration: 0.25,
+  ease: 'easeInOut',
+  width: {
+    duration: 0.25,
+    ease: 'easeInOut',
+  },
+};
+
+export const tabSwitch: Transition = {
+  duration: 0.2,
+  ease: 'easeOut',
+};

src/renderer/lib/utils.ts

@@ -0,0 +1,6 @@
+import { clsx, type ClassValue } from 'clsx';
+import { twMerge } from 'tailwind-merge';
+
+export function cn(...inputs: ClassValue[]): string {
+  return twMerge(clsx(inputs));
+}

src/renderer/main.tsx

@@ -0,0 +1,13 @@
+import React from 'react';
+import ReactDOM from 'react-dom/client';
+import App from './App';
+import { ThemeProvider } from './components/theme-provider';
+import './styles/globals.css';
+
+ReactDOM.createRoot(document.getElementById('root')!).render(
+  <React.StrictMode>
+    <ThemeProvider defaultTheme="dark" attribute="class" enableSystem>
+      <App />
+    </ThemeProvider>
+  </React.StrictMode>
+);

src/renderer/stores/app-store.ts

@@ -0,0 +1,35 @@
+import { create } from 'zustand';
+import { persist } from 'zustand/middleware';
+
+export interface PaneSizes {
+  sidebar: number;
+  editor: number;
+  preview: number;
+}
+
+interface AppState {
+  sidebarVisible: boolean;
+  previewVisible: boolean;
+  zenMode: boolean;
+  paneSizes: PaneSizes;
+  toggleSidebar: () => void;
+  togglePreview: () => void;
+  setZenMode: (value: boolean) => void;
+  setPaneSizes: (sizes: PaneSizes) => void;
+}
+
+export const useAppStore = create<AppState>()(
+  persist(
+    (set) => ({
+      sidebarVisible: true,
+      previewVisible: true,
+      zenMode: false,
+      paneSizes: { sidebar: 20, editor: 50, preview: 30 },
+      toggleSidebar: () => set((s) => ({ sidebarVisible: !s.sidebarVisible })),
+      togglePreview: () => set((s) => ({ previewVisible: !s.previewVisible })),
+      setZenMode: (value) => set({ zenMode: value }),
+      setPaneSizes: (sizes) => set({ paneSizes: sizes }),
+    }),
+    { name: 'mc-app-store' }
+  )
+);

src/renderer/styles/globals.css

@@ -0,0 +1,98 @@
+@tailwind base;
+@tailwind components;
+@tailwind utilities;
+
+@layer base {
+  :root {
+    --background: 0 0% 100%;
+    --foreground: 0 0% 9%;
+    --card: 0 0% 100%;
+    --card-foreground: 0 0% 9%;
+    --popover: 0 0% 100%;
+    --popover-foreground: 0 0% 9%;
+    --primary: 11 79% 51%;
+    --primary-foreground: 0 0% 100%;
+    --secondary: 0 0% 96%;
+    --secondary-foreground: 0 0% 9%;
+    --muted: 0 0% 96%;
+    --muted-foreground: 0 0% 45%;
+    --accent: 0 0% 96%;
+    --accent-foreground: 0 0% 9%;
+    --destructive: 0 84% 60%;
+    --destructive-foreground: 0 0% 100%;
+    --border: 0 0% 90%;
+    --input: 0 0% 90%;
+    --ring: 11 79% 51%;
+    --radius: 0.5rem;
+    --shadow-sm: 0 1px 2px rgba(13, 11, 9, 0.06);
+    --shadow-md: 0 4px 12px rgba(13, 11, 9, 0.08), 0 0 0 1px rgba(13, 11, 9, 0.04);
+    --shadow-lg: 0 12px 32px rgba(13, 11, 9, 0.12), 0 0 0 1px rgba(13, 11, 9, 0.06);
+    --shadow-glow-brand: 0 0 24px rgba(229, 70, 31, 0.25);
+    --glass-bg-light: rgba(255, 255, 255, 0.72);
+    --glass-bg-dark: rgba(13, 11, 9, 0.72);
+    --glass-border-light: rgba(255, 255, 255, 0.4);
+    --glass-border-dark: rgba(255, 255, 255, 0.08);
+  }
+
+  .dark {
+    --background: 30 14% 4%;
+    --foreground: 0 0% 98%;
+    --card: 30 14% 6%;
+    --card-foreground: 0 0% 98%;
+    --popover: 30 14% 6%;
+    --popover-foreground: 0 0% 98%;
+    --primary: 11 79% 51%;
+    --primary-foreground: 0 0% 100%;
+    --secondary: 30 6% 15%;
+    --secondary-foreground: 0 0% 98%;
+    --muted: 30 6% 15%;
+    --muted-foreground: 0 0% 63%;
+    --accent: 30 6% 15%;
+    --accent-foreground: 0 0% 98%;
+    --destructive: 0 62% 30%;
+    --destructive-foreground: 0 0% 100%;
+    --border: 30 6% 15%;
+    --input: 30 6% 15%;
+    --ring: 11 79% 51%;
+    --shadow-sm: 0 1px 2px rgba(13, 11, 9, 0.06);
+    --shadow-md: 0 4px 12px rgba(13, 11, 9, 0.08), 0 0 0 1px rgba(13, 11, 9, 0.04);
+    --shadow-lg: 0 12px 32px rgba(13, 11, 9, 0.12), 0 0 0 1px rgba(13, 11, 9, 0.06);
+    --shadow-glow-brand: 0 0 24px rgba(229, 70, 31, 0.25);
+    --glass-bg-light: rgba(255, 255, 255, 0.72);
+    --glass-bg-dark: rgba(13, 11, 9, 0.72);
+    --glass-border-light: rgba(255, 255, 255, 0.4);
+    --glass-border-dark: rgba(255, 255, 255, 0.08);
+  }
+
+  * {
+    @apply border-border;
+  }
+
+  body {
+    @apply bg-background text-foreground;
+  }
+}
+
+/* Custom scrollbar */
+::-webkit-scrollbar {
+  width: 6px;
+  height: 6px;
+}
+::-webkit-scrollbar-track {
+  background: transparent;
+}
+::-webkit-scrollbar-thumb {
+  background: hsl(var(--muted-foreground) / 0.3);
+  border-radius: 3px;
+}
+::-webkit-scrollbar-thumb:hover {
+  background: hsl(var(--muted-foreground) / 0.5);
+}
+
+/* CodeMirror integration */
+.cm-editor {
+  @apply h-full;
+}
+.cm-editor .cm-scroller {
+  @apply font-mono text-sm;
+}

src/renderer/test/setup.ts

@@ -0,0 +1,35 @@
+import '@testing-library/jest-dom/vitest';
+
+// Mock window.electronAPI for tests
+declare global {
+  interface Window {
+    electronAPI: any;
+  }
+}
+
+if (typeof window !== 'undefined' && !window.electronAPI) {
+  window.electronAPI = {};
+}
+
+// Mock matchMedia for next-themes (jsdom doesn't have it)
+if (typeof window !== 'undefined') {
+  Object.defineProperty(window, 'matchMedia', {
+    writable: true,
+    value: (query: string) => ({
+      matches: false,
+      media: query,
+      onchange: null,
+      addListener: () => {},
+      removeListener: () => {},
+      addEventListener: () => {},
+      removeEventListener: () => {},
+      dispatchEvent: () => true,
+    }),
+  });
+}
+
+// Mock react-resizable-panels for jsdom environment
+if (typeof window !== 'undefined') {
+  Object.defineProperty(window, 'innerWidth', { writable: true, value: 1920 });
+  Object.defineProperty(window, 'innerHeight', { writable: true, value: 1080 });
+}

src/renderer/types/electron.d.ts

@@ -0,0 +1,90 @@
+export interface ElectronAPI {
+  // App info
+  getAppVersion: () => Promise<string>;
+
+  // File operations
+  openFile: () => Promise<{ canceled: boolean; filePaths: string[] }>;
+  saveFile: (data: { path: string; content: string }) => Promise<void>;
+  readFile: (path: string) => Promise<string>;
+  setCurrentFile: (path: string | null) => void;
+
+  // Export
+  exportDocument: (format: string, options?: Record<string, any>) => Promise<void>;
+
+  // Theme
+  getTheme: () => void;
+  onThemeChanged: (callback: (theme: string) => void) => () => void;
+
+  // File events
+  onFileOpened: (callback: (data: { path: string; content: string }) => void) => () => void;
+  onFileNew: (callback: () => void) => () => void;
+  onFileSave: (callback: () => void) => () => void;
+
+  // Conversion status
+  onConversionStatus: (callback: (message: string) => void) => () => void;
+  onConversionComplete: (callback: (data: { format: string; outputPath: string }) => void) => () => void;
+
+  // Dialogs
+  showExportDialog: (format: string) => void;
+  showBatchDialog: () => void;
+  showUniversalConverterDialog: () => void;
+  showTableGenerator: () => void;
+  showPdfEditorDialog: () => void;
+  showHeaderFooterDialog: () => void;
+  showFieldPickerDialog: () => void;
+
+  // Settings
+  getSettings: (key: string) => Promise<any>;
+  setSettings: (key: string, value: any) => Promise<void>;
+
+  // Plugin settings
+  getPluginSetting: (key: string) => Promise<any>;
+  setPluginSetting: (key: string, value: any) => Promise<void>;
+
+  // Sidebar
+  toggleSidebar: () => void;
+  toggleBottomPanel: () => void;
+
+  // Print
+  doPrint: (options?: any) => void;
+
+  // PDF
+  openPdfViewer: (filePath: string) => void;
+  processPdfOperation: (data: any) => void;
+
+  // Images
+  selectFolder: () => Promise<string | null>;
+  savePastedImage: (data: { base64: string; ext: string }) => Promise<{ relativePath: string } | null>;
+
+  // Templates
+  loadTemplate: (file: string) => Promise<string>;
+  getSnippets: () => Promise<any[]>;
+  saveSnippet: (snippet: any) => Promise<void>;
+  deleteSnippet: (id: string) => Promise<void>;
+
+  // Git
+  gitStatus: () => Promise<any>;
+  gitDiff: (file: string) => Promise<any>;
+  gitStage: (files: string[]) => Promise<void>;
+  gitCommit: (message: string) => Promise<void>;
+  gitLog: () => Promise<any[]>;
+
+  // Directory
+  listDirectory: (dir: string) => Promise<any[] | null>;
+  openFilePath: (path: string) => void;
+
+  // Custom CSS
+  selectCustomCSS: () => Promise<string | null>;
+  loadCustomCSS: () => void;
+  clearCustomCSS: () => void;
+
+  // Generic invoke/on
+  invoke: (channel: string, data?: any) => Promise<any>;
+  on: (channel: string, callback: (...args: any[]) => void) => () => void;
+}
+
+declare global {
+  interface Window {
+    electronAPI: ElectronAPI;
+  }
+}

src/renderer/types/ipc.ts

@@ -0,0 +1,62 @@
+export type IpcResult<T> =
+  | { ok: true; data: T }
+  | { ok: false; error: { code: string; message: string } };
+
+export interface FileEntry {
+  name: string;
+  path: string;
+  isDirectory: boolean;
+  size?: number;
+  modifiedAt?: string;
+}
+
+export interface FileResult {
+  path: string;
+  content: string;
+}
+
+export interface PdfOptions {
+  inputPath: string;
+  outputPath: string;
+  format?: 'letter' | 'a4' | 'legal';
+  margins?: { top: number; right: number; bottom: number; left: number };
+  toc?: boolean;
+  embedFonts?: boolean;
+}
+
+export interface DocxOptions {
+  inputPath: string;
+  outputPath: string;
+  template?: string;
+  referenceDoc?: string;
+}
+
+export interface HtmlOptions {
+  inputPath: string;
+  outputPath: string;
+  standalone?: boolean;
+  highlightStyle?: string;
+}
+
+export interface ExportResult {
+  outputPath: string;
+  bytes: number;
+  durationMs: number;
+}
+
+export interface BatchItem {
+  inputPath: string;
+  outputPath: string;
+}
+
+export interface BatchOptions {
+  format: 'pdf' | 'docx' | 'html' | 'png';
+  concurrency?: number;
+}
+
+export interface BatchResult {
+  total: number;
+  succeeded: number;
+  failed: number;
+  results: Array<{ item: BatchItem; ok: boolean; error?: string }>;
+}

src/utils/ModalManager.js

@@ -1,6 +1,6 @@
 /**
  * ModalManager - Unified modal system with accessibility support
- * @version 4.4.3
+ * @version 4.4.2
  */
 class ModalManager {
     #modal;

tailwind.config.js

@@ -0,0 +1,87 @@
+const animate = require('tailwindcss-animate')
+
+/** @type {import('tailwindcss').Config} */
+module.exports = {
+  darkMode: ['class'],
+  content: [
+    './src/renderer/**/*.{js,ts,jsx,tsx}',
+    './src/renderer/index.html',
+  ],
+  theme: {
+    container: {
+      center: true,
+      padding: '2rem',
+      screens: { '2xl': '1400px' },
+    },
+    extend: {
+      colors: {
+        border: 'hsl(var(--border))',
+        input: 'hsl(var(--input))',
+        ring: 'hsl(var(--ring))',
+        background: 'hsl(var(--background))',
+        foreground: 'hsl(var(--foreground))',
+        primary: {
+          DEFAULT: 'hsl(var(--primary))',
+          foreground: 'hsl(var(--primary-foreground))',
+        },
+        secondary: {
+          DEFAULT: 'hsl(var(--secondary))',
+          foreground: 'hsl(var(--secondary-foreground))',
+        },
+        destructive: {
+          DEFAULT: 'hsl(var(--destructive))',
+          foreground: 'hsl(var(--destructive-foreground))',
+        },
+        muted: {
+          DEFAULT: 'hsl(var(--muted))',
+          foreground: 'hsl(var(--muted-foreground))',
+        },
+        accent: {
+          DEFAULT: 'hsl(var(--accent))',
+          foreground: 'hsl(var(--accent-foreground))',
+        },
+        popover: {
+          DEFAULT: 'hsl(var(--popover))',
+          foreground: 'hsl(var(--popover-foreground))',
+        },
+        card: {
+          DEFAULT: 'hsl(var(--card))',
+          foreground: 'hsl(var(--card-foreground))',
+        },
+        brand: {
+          DEFAULT: '#e5461f',
+          dark: '#c93a18',
+          light: '#ff6b47',
+        },
+        success: '#1a7a56',
+        warning: 'hsl(45 93% 47%)',
+        danger: 'hsl(0 84% 60%)',
+        info: 'hsl(199 89% 48%)',
+        warm: {
+          50: '#fafbfc', 100: '#f5f5f5', 200: '#e3e3e3', 300: '#d1d1d1',
+          400: '#b0b0b0', 500: '#9a9696', 600: '#7a7878', 700: '#5a5858',
+          800: '#4e4e4e', 900: '#464646', 950: '#0d0b09',
+        },
+      },
+      borderRadius: {
+        lg: 'var(--radius)',
+        md: 'calc(var(--radius) - 2px)',
+        sm: 'calc(var(--radius) - 4px)',
+      },
+      fontFamily: {
+        sans: ['"Plus Jakarta Sans"', 'system-ui', 'sans-serif'],
+        display: ['"Barlow Condensed"', 'system-ui', 'sans-serif'],
+        mono: ['"JetBrains Mono"', '"Fira Code"', '"SF Mono"', 'Consolas', 'monospace'],
+      },
+      keyframes: {
+        'accordion-down': { from: { height: '0' }, to: { height: 'var(--radix-accordion-content-height)' } },
+        'accordion-up': { from: { height: 'var(--radix-accordion-content-height)' }, to: { height: '0' } },
+      },
+      animation: {
+        'accordion-down': 'accordion-down 0.2s ease-out',
+        'accordion-up': 'accordion-up 0.2s ease-out',
+      },
+    },
+  },
+  plugins: [animate],
+}

tests/component/layout/AppHeader.test.tsx

@@ -0,0 +1,33 @@
+import { describe, it, expect, beforeEach } from 'vitest';
+import { render, screen } from '@testing-library/react';
+import userEvent from '@testing-library/user-event';
+import { ThemeProvider } from '@/components/theme-provider';
+import { AppHeader } from '@/components/layout/AppHeader';
+import { useAppStore } from '@/stores/app-store';
+
+describe('AppHeader', () => {
+  beforeEach(() => {
+    localStorage.clear();
+    useAppStore.setState({ sidebarVisible: true, previewVisible: true, zenMode: false });
+  });
+
+  it('renders the app title', () => {
+    render(
+      <ThemeProvider defaultTheme="dark" attribute="class">
+        <AppHeader />
+      </ThemeProvider>
+    );
+    expect(screen.getByText(/markdownconverter/i)).toBeInTheDocument();
+  });
+
+  it('toggles sidebar when sidebar button clicked', async () => {
+    render(
+      <ThemeProvider defaultTheme="dark" attribute="class">
+        <AppHeader />
+      </ThemeProvider>
+    );
+    const btn = screen.getByRole('button', { name: /toggle sidebar/i });
+    await userEvent.click(btn);
+    expect(useAppStore.getState().sidebarVisible).toBe(false);
+  });
+});

tests/component/layout/AppShell.test.tsx

@@ -0,0 +1,49 @@
+import { describe, it, expect, beforeEach, vi } from 'vitest';
+import { render, screen } from '@testing-library/react';
+import { ThemeProvider } from '@/components/theme-provider';
+import { AppShell } from '@/components/layout/AppShell';
+import { useAppStore } from '@/stores/app-store';
+
+// Mock react-resizable-panels for jsdom environment
+vi.mock('@/components/ui/resizable', () => ({
+  ResizablePanelGroup: ({ children, direction, onLayout }: any) => (
+    <div data-testid="resizable-panel-group" data-direction={direction}>
+      {children}
+    </div>
+  ),
+  ResizablePanel: ({ children, defaultSize, minSize, maxSize }: any) => (
+    <div data-testid="resizable-panel" data-size={defaultSize} data-min={minSize} data-max={maxSize}>
+      {children}
+    </div>
+  ),
+  ResizableHandle: () => <div data-testid="resizable-handle" />,
+}));
+
+describe('AppShell', () => {
+  beforeEach(() => {
+    localStorage.clear();
+    useAppStore.setState({ sidebarVisible: true, previewVisible: true, zenMode: false });
+  });
+
+  it('renders all shell surfaces when sidebar and preview are visible', () => {
+    render(
+      <ThemeProvider defaultTheme="dark" attribute="class">
+        <AppShell />
+      </ThemeProvider>
+    );
+    expect(screen.getByText(/markdownconverter/i)).toBeInTheDocument();
+    expect(screen.getByText(/no files open/i)).toBeInTheDocument();
+    expect(screen.getByText(/no file selected/i)).toBeInTheDocument();
+    expect(screen.getByText(/0 words/i)).toBeInTheDocument();
+  });
+
+  it('hides sidebar when sidebarVisible is false', () => {
+    useAppStore.setState({ sidebarVisible: false });
+    render(
+      <ThemeProvider defaultTheme="dark" attribute="class">
+        <AppShell />
+      </ThemeProvider>
+    );
+    expect(screen.queryByText(/file tree placeholder/i)).not.toBeInTheDocument();
+  });
+});

tests/component/layout/StatusBar.test.tsx

@@ -0,0 +1,10 @@
+import { describe, it, expect } from 'vitest';
+import { render, screen } from '@testing-library/react';
+import { StatusBar } from '@/components/layout/StatusBar';
+
+describe('StatusBar', () => {
+  it('renders zero word count when no file is open', () => {
+    render(<StatusBar />);
+    expect(screen.getByText(/0 words/i)).toBeInTheDocument();
+  });
+});

tests/component/layout/TabBar.test.tsx

@@ -0,0 +1,10 @@
+import { describe, it, expect } from 'vitest';
+import { render, screen } from '@testing-library/react';
+import { TabBar } from '@/components/layout/TabBar';
+
+describe('TabBar', () => {
+  it('renders an empty state when no tabs are open', () => {
+    render(<TabBar />);
+    expect(screen.getByText(/no files open/i)).toBeInTheDocument();
+  });
+});

tests/component/layout/Toolbar.test.tsx

@@ -0,0 +1,11 @@
+import { describe, it, expect } from 'vitest';
+import { render, screen } from '@testing-library/react';
+import { Toolbar } from '@/components/layout/Toolbar';
+
+describe('Toolbar', () => {
+  it('renders formatting buttons', () => {
+    render(<Toolbar />);
+    expect(screen.getByRole('button', { name: /bold/i })).toBeInTheDocument();
+    expect(screen.getByRole('button', { name: /italic/i })).toBeInTheDocument();
+  });
+});

tests/component/theme-toggle.test.tsx

@@ -0,0 +1,40 @@
+import { describe, it, expect, beforeEach } from 'vitest';
+import { render, screen } from '@testing-library/react';
+import userEvent from '@testing-library/user-event';
+import { ThemeProvider } from '@/components/theme-provider';
+import { ThemeToggle } from '@/components/theme-toggle';
+
+Object.defineProperty(window, 'matchMedia', {
+  writable: true,
+  value: vi.fn().mockImplementation((query) => ({
+    matches: false,
+    media: query,
+    onchange: null,
+    addListener: vi.fn(),
+    removeListener: vi.fn(),
+    addEventListener: vi.fn(),
+    removeEventListener: vi.fn(),
+    dispatchEvent: vi.fn(),
+  })),
+});
+
+describe('ThemeToggle', () => {
+  beforeEach(() => {
+    localStorage.clear();
+    document.documentElement.classList.remove('dark', 'light');
+  });
+
+  it('toggles between light and dark when clicked', async () => {
+    render(
+      <ThemeProvider defaultTheme="light" attribute="class">
+        <ThemeToggle />
+      </ThemeProvider>
+    );
+    const btn = screen.getByRole('button');
+    expect(btn).toHaveAccessibleName(/toggle theme/i);
+    await userEvent.click(btn);
+    expect(document.documentElement.classList.contains('dark')).toBe(true);
+    await userEvent.click(btn);
+    expect(document.documentElement.classList.contains('light')).toBe(true);
+  });
+});

tests/component/ui/button.test.tsx

@@ -0,0 +1,24 @@
+import { describe, it, expect } from 'vitest';
+import { render, screen } from '@testing-library/react';
+import userEvent from '@testing-library/user-event';
+import { Button } from '@/components/ui/button';
+
+describe('Button', () => {
+  it('renders children', () => {
+    render(<Button>Click me</Button>);
+    expect(screen.getByRole('button', { name: /click me/i })).toBeInTheDocument();
+  });
+
+  it('calls onClick when clicked', async () => {
+    let count = 0;
+    render(<Button onClick={() => count++}>+</Button>);
+    await userEvent.click(screen.getByRole('button'));
+    expect(count).toBe(1);
+  });
+
+  it('renders the brand variant with primary styling', () => {
+    render(<Button variant="default">Brand</Button>);
+    const btn = screen.getByRole('button');
+    expect(btn.className).toContain('bg-primary');
+  });
+});

tests/unit/lib/cn.test.ts

@@ -0,0 +1,20 @@
+import { describe, it, expect } from 'vitest';
+import { cn } from '@/lib/utils';
+
+describe('cn', () => {
+  it('merges class names', () => {
+    expect(cn('a', 'b')).toBe('a b');
+  });
+
+  it('deduplicates conflicting tailwind classes', () => {
+    expect(cn('p-2', 'p-4')).toBe('p-4');
+  });
+
+  it('ignores falsy values', () => {
+    expect(cn('a', false, null, undefined, '', 'b')).toBe('a b');
+  });
+
+  it('accepts conditional class objects', () => {
+    expect(cn('base', { active: true, disabled: false })).toBe('base active');
+  });
+});

tests/unit/lib/ipc.test.ts

@@ -0,0 +1,41 @@
+import { describe, it, expect, beforeEach, vi } from 'vitest';
+import { ipc } from '@/lib/ipc';
+import type { FileResult } from '@/types/ipc';
+
+describe('ipc wrapper', () => {
+  beforeEach(() => {
+    window.electronAPI = {
+      file: {
+        read: vi.fn().mockResolvedValue('# hello'),
+        write: vi.fn().mockResolvedValue(undefined),
+        list: vi.fn().mockResolvedValue([]),
+      },
+    };
+  });
+
+  it('file.read returns ok result on success', async () => {
+    const result = await ipc.file.read('/foo.md');
+    expect(result.ok).toBe(true);
+    if (result.ok) {
+      expect(result.data).toBe('# hello');
+    }
+  });
+
+  it('file.read returns err result when channel throws', async () => {
+    window.electronAPI.file.read = vi.fn().mockRejectedValue(new Error('ENOENT'));
+    const result = await ipc.file.read('/missing.md');
+    expect(result.ok).toBe(false);
+    if (!result.ok) {
+      expect(result.error.message).toBe('ENOENT');
+    }
+  });
+
+  it('file.read returns err result when channel missing', async () => {
+    delete (window.electronAPI.file as any).read;
+    const result = await ipc.file.read('/foo.md');
+    expect(result.ok).toBe(false);
+    if (!result.ok) {
+      expect(result.error.code).toBe('CHANNEL_MISSING');
+    }
+  });
+});

tests/unit/lib/motion.test.ts

@@ -0,0 +1,32 @@
+import { describe, it, expect } from 'vitest';
+import {
+  fadeIn,
+  slideInRight,
+  modalPop,
+  toastSpring,
+  sidebarToggle,
+} from '@/lib/motion';
+
+describe('motion presets', () => {
+  it('fadeIn is a valid transition object', () => {
+    expect(fadeIn.duration).toBeGreaterThan(0);
+    expect(fadeIn.ease).toBeDefined();
+  });
+
+  it('slideInRight uses translateX transform', () => {
+    expect(slideInRight.x).toBe('100%');
+  });
+
+  it('modalPop uses scale and opacity', () => {
+    expect(modalPop.scale).toBeDefined();
+    expect(modalPop.opacity).toBeDefined();
+  });
+
+  it('toastSpring has spring physics', () => {
+    expect(toastSpring.type).toBe('spring');
+  });
+
+  it('sidebarToggle animates width', () => {
+    expect(sidebarToggle.width.duration).toBeGreaterThan(0);
+  });
+});

tests/unit/stores/app-store.test.ts

@@ -0,0 +1,35 @@
+import { describe, it, expect, beforeEach } from 'vitest';
+import { useAppStore } from '@/stores/app-store';
+
+describe('useAppStore', () => {
+  beforeEach(() => {
+    localStorage.clear();
+    useAppStore.setState({
+      sidebarVisible: true,
+      previewVisible: true,
+      zenMode: false,
+      paneSizes: { sidebar: 20, editor: 50, preview: 30 },
+    });
+  });
+
+  it('toggles sidebar visibility', () => {
+    expect(useAppStore.getState().sidebarVisible).toBe(true);
+    useAppStore.getState().toggleSidebar();
+    expect(useAppStore.getState().sidebarVisible).toBe(false);
+  });
+
+  it('toggles preview visibility', () => {
+    useAppStore.getState().togglePreview();
+    expect(useAppStore.getState().previewVisible).toBe(false);
+  });
+
+  it('updates pane sizes', () => {
+    useAppStore.getState().setPaneSizes({ sidebar: 25, editor: 50, preview: 25 });
+    expect(useAppStore.getState().paneSizes).toEqual({ sidebar: 25, editor: 50, preview: 25 });
+  });
+
+  it('enables and disables zen mode', () => {
+    useAppStore.getState().setZenMode(true);
+    expect(useAppStore.getState().zenMode).toBe(true);
+  });
+});

vite.renderer.config.ts

@@ -0,0 +1,23 @@
+import { defineConfig } from 'vite';
+import react from '@vitejs/plugin-react';
+import path from 'path';
+
+export default defineConfig({
+  plugins: [react()],
+  root: path.join(__dirname, 'src/renderer'),
+  base: './',
+  build: {
+    outDir: path.join(__dirname, 'dist/renderer'),
+    emptyOutDir: true,
+    sourcemap: true,
+  },
+  resolve: {
+    alias: {
+      '@': path.join(__dirname, 'src/renderer'),
+    },
+  },
+  server: {
+    port: 5173,
+    strictPort: true,
+  },
+});

vitest.config.ts

@@ -0,0 +1,23 @@
+import { defineConfig } from 'vitest/config';
+import react from '@vitejs/plugin-react';
+import path from 'path';
+
+export default defineConfig({
+  plugins: [react()],
+  test: {
+    environment: 'jsdom',
+    globals: true,
+    setupFiles: ['./src/renderer/test/setup.ts'],
+    include: ['tests/**/*.{test,spec}.{ts,tsx}'],
+    coverage: {
+      provider: 'v8',
+      include: ['src/renderer/**/*.{ts,tsx}'],
+      exclude: ['src/renderer/test/**', 'src/renderer/**/*.test.*'],
+    },
+  },
+  resolve: {
+    alias: {
+      '@': path.join(__dirname, 'src/renderer'),
+    },
+  },
+});