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/renderer/components/AboutDialog/AboutDialog.tsx

@@ -1,55 +1,56 @@
-import React from 'react'
-import { AppIcon, Gitee } from '../Icons'
-
-const APP_VERSION = 'v0.3.2'
-
-interface AboutDialogProps {
-  onClose: () => void
-}
-
-export const AboutDialog = React.memo(function AboutDialog({ onClose }: AboutDialogProps) {
-  const handleLinkClick = (e: React.MouseEvent<HTMLAnchorElement>): void => {
-    e.preventDefault()
-    if (window.electronAPI?.openExternal) {
-      window.electronAPI.openExternal('https://gitee.com/thzxx/MarkLite')
-    } else {
-      window.open('https://gitee.com/thzxx/MarkLite', '_blank')
-    }
-  }
-
-  return (
-    <div className="about-overlay" onClick={onClose} role="dialog" aria-modal="true" aria-label="关于 MarkLite">
-      <div className="about-dialog" onClick={(e: React.MouseEvent) => e.stopPropagation()}>
-        <div className="about-header">
-          <AppIcon size={64} />
-          <h2>MarkLite</h2>
-          <span className="about-version">{APP_VERSION}</span>
-        </div>
-        <div className="about-body">
-          <p>一款轻量级的 Windows 本地 Markdown 编辑器</p>
-          <div className="about-features">
-            <span>多标签页</span>
-            <span>实时预览</span>
-            <span>代码高亮</span>
-            <span>暗色主题</span>
-            <span>拖拽打开</span>
-            <span>搜索替换</span>
-            <span>文件树</span>
-            <span>状态持久化</span>
-          </div>
-        </div>
-        <div className="about-footer">
-          <a className="about-link" href="#" onClick={handleLinkClick}>
-            <Gitee size={16} />
-            <span>gitee.com/thzxx/MarkLite</span>
-          </a>
-          <p>基于 Electron + React + TypeScript 构建</p>
-          <p className="about-copyright">© 2026 thzxx</p>
-        </div>
-        <button className="about-close-btn" onClick={onClose}>关闭</button>
-      </div>
-    </div>
-  )
-})
-
-AboutDialog.displayName = 'AboutDialog'
+import React from 'react'
+import { AppIcon, Gitee } from '../Icons'
+
+const APP_VERSION = 'v0.3.4'
+
+interface AboutDialogProps {
+  onClose: () => void
+}
+
+export const AboutDialog = React.memo(function AboutDialog({ onClose }: AboutDialogProps) {
+  const handleLinkClick = (e: React.MouseEvent<HTMLAnchorElement>): void => {
+    e.preventDefault()
+    if (window.electronAPI?.openExternal) {
+      window.electronAPI.openExternal('https://gitee.com/thzxx/MarkLite')
+    } else {
+      window.open('https://gitee.com/thzxx/MarkLite', '_blank')
+    }
+  }
+
+  return (
+    <div className="about-overlay" onClick={onClose} role="dialog" aria-modal="true" aria-label="关于 MarkLite">
+      <div className="about-dialog" onClick={(e: React.MouseEvent) => e.stopPropagation()}>
+        <div className="about-header">
+          <AppIcon size={64} />
+          <h2>MarkLite</h2>
+          <span className="about-version">{APP_VERSION}</span>
+        </div>
+        <div className="about-body">
+          <p>一款轻量级的 Windows 本地 Markdown 编辑器</p>
+          <div className="about-features">
+            <span>多标签页</span>
+            <span>实时预览</span>
+            <span>代码高亮</span>
+            <span>暗色主题</span>
+            <span>拖拽打开</span>
+            <span>搜索替换</span>
+            <span>文件树</span>
+            <span>文档大纲</span>
+            <span>状态持久化</span>
+          </div>
+        </div>
+        <div className="about-footer">
+          <a className="about-link" href="#" onClick={handleLinkClick}>
+            <Gitee size={16} />
+            <span>gitee.com/thzxx/MarkLite</span>
+          </a>
+          <p>基于 Electron + React + TypeScript 构建</p>
+          <p className="about-copyright">© 2026 thzxx</p>
+        </div>
+        <button className="about-close-btn" onClick={onClose}>关闭</button>
+      </div>
+    </div>
+  )
+})
+
+AboutDialog.displayName = 'AboutDialog'