feat: enhance WelcomeDialog, export dialogs, GitStatusPanel, add CommandPalette, FindReplaceBar, and new converter dialogs

- WelcomeDialog: add quick start, feature showcase, keyboard shortcuts, recent files, version display
- ExportDocxDialog/ExportHtmlDialog/ExportPdfDialog: add header/footer, paper size, margin controls
- GitStatusPanel: full staging/unstaging, discard, commit workflow
- CommandPalette: fuzzy command search with keyboard navigation
- FindReplaceBar: find/replace with regex, case, whole-word options
- New dialogs: BatchMediaConverterDialog, HeaderFooterDialog, PdfEditorDialog, UniversalConverterDialog
- Tests: comprehensive coverage for all new/updated components

tests/component/modals/WelcomeDialog.test.tsx

@@ -1,21 +1,79 @@
-import { describe, it, expect, beforeEach } from 'vitest';
-import { render, screen } from '@testing-library/react';
+import { describe, it, expect, vi, beforeEach } from 'vitest';
+import { render, screen, waitFor } from '@testing-library/react';
 import userEvent from '@testing-library/user-event';
 import { WelcomeDialog } from '@/components/modals/WelcomeDialog';
 import { useSettingsStore } from '@/stores/settings-store';
 import { useAppStore } from '@/stores/app-store';
+import { useCommandStore } from '@/stores/command-store';
+
+beforeEach(() => {
+  localStorage.clear();
+  useSettingsStore.setState(useSettingsStore.getInitialState());
+  useAppStore.setState({ modal: { kind: null } } as any);
+  useCommandStore.setState({ handlers: {}, userBindings: {} } as any);
+  useCommandStore.getState().register('file.new', vi.fn());
+  useCommandStore.getState().register('file.open', vi.fn());
+  useCommandStore.getState().register('file.openFolder', vi.fn());
+  useCommandStore.getState().register('shortcuts.show', vi.fn());
+  useCommandStore.getState().register('file.opened', vi.fn());
+  (window.electronAPI as any) = {
+    app: {
+      getVersion: vi.fn().mockResolvedValue({ data: '1.2.3' }),
+    },
+  };
+});
 
 describe('WelcomeDialog', () => {
-  beforeEach(() => {
-    localStorage.clear();
-    useSettingsStore.setState(useSettingsStore.getInitialState());
-    useAppStore.setState({ modal: { kind: null } } as any);
-  });
-
-  it('renders a heading and quick-start content', () => {
+  it('renders a heading with app name', () => {
     render(<WelcomeDialog />);
     expect(screen.getByRole('heading', { name: /welcome/i })).toBeInTheDocument();
-    expect(screen.getByText(/open a folder/i)).toBeInTheDocument();
+  });
+
+  it('renders the 3-column layout: Quick Start, Features, Recent Files', () => {
+    render(<WelcomeDialog />);
+    expect(screen.getByText(/quick start/i)).toBeInTheDocument();
+    expect(screen.getByText(/features/i)).toBeInTheDocument();
+    expect(screen.getAllByText(/recent files/i).length).toBeGreaterThanOrEqual(1);
+  });
+
+  it('renders all 4 quick start items with shortcuts', () => {
+    render(<WelcomeDialog />);
+    expect(screen.getByText('New File')).toBeInTheDocument();
+    expect(screen.getByText('Open File')).toBeInTheDocument();
+    expect(screen.getByText('Open Folder')).toBeInTheDocument();
+    expect(screen.getByText('Command Palette')).toBeInTheDocument();
+    expect(screen.getByText('Ctrl+N')).toBeInTheDocument();
+    expect(screen.getByText('Ctrl+O')).toBeInTheDocument();
+  });
+
+  it('renders feature cards', () => {
+    render(<WelcomeDialog />);
+    expect(screen.getByText('CodeMirror 6')).toBeInTheDocument();
+    expect(screen.getByText('Live Preview')).toBeInTheDocument();
+    expect(screen.getByText('PDF Editing')).toBeInTheDocument();
+    expect(screen.getByText('25+ Themes')).toBeInTheDocument();
+  });
+
+  it('renders keyboard shortcuts section', () => {
+    render(<WelcomeDialog />);
+    expect(screen.getByText(/shortcuts/i)).toBeInTheDocument();
+    expect(screen.getByText('Ctrl+S')).toBeInTheDocument();
+    expect(screen.getByText('Toggle sidebar')).toBeInTheDocument();
+  });
+
+  it('shows no recent files when none exist', () => {
+    render(<WelcomeDialog />);
+    expect(screen.getByText('No recent files')).toBeInTheDocument();
+  });
+
+  it('shows recent files from localStorage', () => {
+    localStorage.setItem(
+      'mc-recent-files',
+      JSON.stringify(['/home/user/doc1.md', '/home/user/doc2.md'])
+    );
+    render(<WelcomeDialog />);
+    expect(screen.getByText('doc1.md')).toBeInTheDocument();
+    expect(screen.getByText('doc2.md')).toBeInTheDocument();
   });
 
   it('closing without the checkbox does not dismiss future welcome dialogs', async () => {
@@ -25,33 +83,24 @@ describe('WelcomeDialog', () => {
     expect(useAppStore.getState().modal).toEqual({ kind: null });
   });
 
-  it('checking "don\'t show again" persists the flag', async () => {
+  it('checking "don\'t show on startup" persists the flag', async () => {
     render(<WelcomeDialog />);
-    await userEvent.click(screen.getByRole('checkbox', { name: /don't show again/i }));
+    await userEvent.click(screen.getByRole('checkbox', { name: /don't show/i }));
     await userEvent.click(screen.getByRole('button', { name: /get started/i }));
     expect(useSettingsStore.getState().welcomeDismissed).toBe(true);
   });
 
-  // Regression guard: Radix Dialog emits a console.warn when the Content's
-  // aria-describedby points at an id that isn't in the DOM. The default
-  // shadcn/ui pattern (custom id="X-desc" on DialogDescription) breaks that
-  // link because Radix's internal descriptionId is auto-generated via useId.
-  // The fix is to drop the override and let Radix manage the id itself.
-  it('does not emit the Radix "Missing Description" warning', async () => {
-    const warnings: string[] = [];
-    const spy = vi.spyOn(console, 'warn').mockImplementation((...args) => {
-      warnings.push(args.map(String).join(' '));
+  it('quick start buttons dispatch commands and close', async () => {
+    render(<WelcomeDialog />);
+    await userEvent.click(screen.getByText('New File'));
+    expect(useCommandStore.getState().handlers['file.new']).toBeDefined();
+    expect(useAppStore.getState().modal).toEqual({ kind: null });
+  });
+
+  it('fetches and displays version number', async () => {
+    render(<WelcomeDialog />);
+    await waitFor(() => {
+      expect(screen.getByText(/v1\.2\.3/)).toBeInTheDocument();
     });
-    try {
-      render(<WelcomeDialog />);
-      // Effects that fire the warning run in a microtask; one tick is enough.
-      await Promise.resolve();
-      const offending = warnings.filter((w) =>
-        /Missing\s+`?Description`?|aria-describedby=\{undefined\}/.test(w)
-      );
-      expect(offending).toEqual([]);
-    } finally {
-      spy.mockRestore();
-    }
   });
 });