v0.3.4: Bug修复+性能优化+文档大纲功能

🔴 Bug修复 (6):
- Sidebar反斜杠正则修复 (Windows路径规范化)
- FileWatcher文件删除后自动恢复监听
- SearchReplace replaceAll防过期匹配位置
- openFolderDialog null结果守卫
- 保存异常时空路径保护
- Markdown绝对路径图片拼接修复

🟡 性能优化:
- Editor切换标签时内容比较，相同跳过replaceAll

🔵 代码质量:
- 创建共享常量模块 src/shared/constants.ts，消除双副本

🎯 新增功能:
- 文档大纲 (Table of Contents) — 侧边栏标题导航

🔧 换行符统一: CRLF → LF

src/main/file-watcher.ts

@@ -24,12 +24,22 @@ export class FileWatcher {
       })
       // L-02: 监听 error 事件，文件被删除时显式关闭并清理状态
       this.watcher.on('error', () => {
-        if (this.watcher) {
-          this.watcher.close()
-          this.watcher = null
+        this.stop()
+        const originalPath = this.currentPath
+        if (originalPath) {
+          const pollInterval = setInterval(() => {
+            try {
+              if (fs.existsSync(originalPath)) {
+                clearInterval(pollInterval)
+                this.start(originalPath)
+              }
+            } catch {
+              clearInterval(pollInterval)
+            }
+          }, 2000)
+          // 最多轮询30秒
+          setTimeout(() => clearInterval(pollInterval), 30000)
         }
-        this.currentPath = null
-        this.isSelfWriting = false
       })
     } catch {
       // silently ignore