build(identity): rename to Markdown Converter React + defaults

- package.json: name -> markdown-converter-react; productName -> Markdown
  Converter React; appId -> com.concreteinfo.markdownconverter.react;
  linux.executableName -> markdown-converter-react
- Window title: 'Markdown Converter — React Dev' in dev mode
- Migration defaults: monospaceFont, monospaceLigatures, appVariant
- Bumped fields in v5OnlyFields so v4->v5 detection covers new keys

src/main/updater/migration-transform.js

@@ -39,6 +39,9 @@ const v5SettingsSchema = z
     updateChannel: z.enum(['github', 'concreteinfo']).default('github'),
     autoCheckUpdates: z.boolean().default(true),
     firstRun: z.boolean().default(true),
+    monospaceFont: z.enum(['jetbrains-mono', 'fira-code']).default('jetbrains-mono'),
+    monospaceLigatures: z.boolean().default(false),
+    appVariant: z.enum(['classic', 'react']).default('react'),
     'migration.version': z.literal(5).optional(),
   })
   .passthrough();

src/main/window/index.js

@@ -9,12 +9,14 @@ const menu = require('../menu');
 
 function createMainWindow() {
   const bounds = state.load();
+  const isDev = !!process.env.VITE_DEV_SERVER_URL;
   const win = new BrowserWindow({
     width: bounds.width,
     height: bounds.height,
     x: bounds.x,
     y: bounds.y,
     show: true,
+    title: `Markdown Converter${isDev ? ' — React Dev' : ''}`,
     webPreferences: {
       // The preload script exposes `window.electronAPI` — the only IPC
       // bridge the renderer uses. Without this, every renderer call returns

src/renderer/lib/migrations/v4-to-v5.ts

@@ -10,7 +10,7 @@ export const v4SettingsSchema = z.object({
   snippets: z.array(z.unknown()).default([]),
 });
 
-const v5OnlyFields = ['updateChannel', 'autoCheckUpdates', 'firstRun'];
+const v5OnlyFields = ['updateChannel', 'autoCheckUpdates', 'firstRun', 'monospaceFont', 'monospaceLigatures', 'appVariant'];
 const v5ThemeValues = ['light', 'dark', 'system'] as const;
 
 function isAlreadyV5(data: unknown): boolean {