refactor: v2.0 全量重构 — TypeScript + React + Zustand + IndexedDB

技术栈升级：
- JavaScript → TypeScript 5.6（全量类型安全）
- 原生 DOM → React 18（函数组件 + Hooks）
- 全局变量 → Zustand 5（轻量状态管理）
- localStorage → IndexedDB / Dexie.js 4（大容量、异步、索引）
- marked.js → unified / remark / rehype（插件化渲染管线）
- 无打包 → electron-vite 3（HMR 热更新）
- 纯 CSS → CSS Variables + CSS Modules

新增功能：
- 标签页状态 IndexedDB 持久化（关闭后可恢复）
- 最近打开文件列表
- 大文件虚拟化行号（>2000 行）
- 搜索高亮二分查找优化 O(log N)
- rehype-sanitize HTML 安全过滤

文件结构：
- 7 个源文件 → 51 个模块化文件
- src/main/     主进程（6 文件）
- src/preload/  预加载（1 文件）
- src/renderer/ 渲染进程（42 文件：组件/hooks/stores/lib/db/types/styles）
- src/shared/   共享类型（2 文件）

构建验证：
- TypeScript 检查零错误
- electron-vite build 成功
- 产物：main 15kB + preload 2kB + renderer 1.5MB

src/renderer/types/file.ts

@@ -0,0 +1,13 @@
+export interface FileNode {
+  name: string
+  path: string
+  type: 'file' | 'dir'
+  children?: FileNode[]
+}
+
+export interface DirTreeResult {
+  success: boolean
+  tree?: FileNode[]
+  rootPath?: string
+  error?: string
+}

src/renderer/types/index.ts

@@ -0,0 +1,5 @@
+export type { Tab } from './tab'
+export type { FileNode, DirTreeResult } from './file'
+export type { ViewMode, Settings } from './settings'
+export type { SearchMatch, SearchOptions } from './search'
+export type { ElectronAPI, IpcInvokeMap } from './ipc'

src/renderer/types/ipc.ts

@@ -0,0 +1,59 @@
+import type {
+  OpenFileResponse,
+  ReadFileResult,
+  SaveFilePayload,
+  SaveFileResult,
+  SaveAsPayload,
+  ReloadFileResult,
+  FileStatsResult,
+  ReadDirTreeResult
+} from '../../shared/types'
+
+export interface IpcInvokeMap {
+  'dialog:openFile': [void, OpenFileResponse]
+  'file:read': [string, ReadFileResult]
+  'file:save': [SaveFilePayload, SaveFileResult]
+  'file:saveAs': [SaveAsPayload, SaveFileResult]
+  'file:getCurrentPath': [void, string | null]
+  'file:stats': [string, FileStatsResult]
+  'file:reload': [void, ReloadFileResult]
+  'tab:switched': [string | null, void]
+  'window:forceClose': [void, void]
+  'window:cancelClose': [void, void]
+  'dir:readTree': [string, ReadDirTreeResult]
+  'dir:openDialog': [void, string | null]
+  'dir:watch': [string, void]
+  'dir:unwatch': [void, void]
+}
+
+export interface ElectronAPI {
+  openFile: () => Promise<OpenFileResponse>
+  readFile: (filePath: string) => Promise<ReadFileResult>
+  saveFile: (data: SaveFilePayload) => Promise<SaveFileResult>
+  saveFileAs: (data: SaveAsPayload) => Promise<SaveFileResult>
+  getCurrentPath: () => Promise<string | null>
+  getFileStats: (filePath: string) => Promise<FileStatsResult>
+  reloadFile: () => Promise<ReloadFileResult>
+  tabSwitched: (filePath: string | null) => Promise<void>
+  forceClose: () => Promise<void>
+  cancelClose: () => Promise<void>
+  openExternal: (url: string) => void
+  readDirTree: (dirPath: string) => Promise<ReadDirTreeResult>
+  openFolderDialog: () => Promise<string | null>
+  watchDir: (dirPath: string) => Promise<void>
+  unwatchDir: () => Promise<void>
+  onFileOpenInTab: (callback: (data: { filePath: string; content: string }) => void) => void
+  onMenuSave: (callback: () => void) => void
+  onMenuSaveAs: (callback: () => void) => void
+  onViewModeChange: (callback: (mode: string) => void) => void
+  onExternalModification: (callback: (filePath: string) => void) => void
+  onDirChanged: (callback: () => void) => void
+  onConfirmClose: (callback: () => void) => void
+  removeAllListeners: (channel: string) => void
+}
+
+declare global {
+  interface Window {
+    electronAPI?: ElectronAPI
+  }
+}

src/renderer/types/search.ts

@@ -0,0 +1,9 @@
+export interface SearchMatch {
+  start: number
+  end: number
+}
+
+export interface SearchOptions {
+  caseSensitive: boolean
+  useRegex: boolean
+}

src/renderer/types/settings.ts

@@ -0,0 +1,17 @@
+export type ViewMode = 'split' | 'editor' | 'preview'
+
+export interface Settings {
+  darkMode: boolean
+  viewMode: ViewMode
+  splitRatio: number
+  sidebarCollapsed: boolean
+  sidebarWidth: number
+}
+
+export const DEFAULT_SETTINGS: Settings = {
+  darkMode: false,
+  viewMode: 'split',
+  splitRatio: 50,
+  sidebarCollapsed: false,
+  sidebarWidth: 240
+}

src/renderer/types/tab.ts

@@ -0,0 +1,11 @@
+export interface Tab {
+  id: string
+  filePath: string | null
+  content: string
+  isModified: boolean
+  scrollTop: number
+  scrollLeft: number
+  selectionStart: number
+  selectionEnd: number
+  previewScrollTop: number
+}