v0.3.10: 全面优化增强 — 17项Bug修复/稳定性/功能改进

P0 致命Bug修复:
- A1: openFolderDialog 类型/运行时崩溃(文件夹打开功能完全失效)
- A2: SourceEditor 受控textarea手动改DOM反模式
- A3: tabStore.updateTabContent 内容相同时误标isModified

死代码清理:
- B1: 删除menu:*/save/as/viewMode 三个永不触发的IPC通道

健壮性修复:
- E1: rehypeFixImages 路径规范化+防越界加固
- E2: getFileName 尾斜杠返回正确文件名
- E3: EditorToolbar 行内代码按钮改用toggleInlineCodeCommand
- E4: ErrorBoundary 内联样式抽为CSS类

功能增强:
- D1: 标签页拖拽排序(tabStore.moveTab + TabBar DnD + CSS)
- D2: Milkdown自动配对括号/引号(ProseMirror插件)
- D3: 状态栏自动保存开关可点击
- D4: 文档大纲活跃标题高亮(useActiveHeading hook)
- D5: 关闭窗口前flush防抖数据(flushSaveToDB)
- D6: 搜索替换支持正则表达式

类型/架构:
- C2: preload类型集中定义(ElectronAPI契约)
- __pycache__ typo修复

文档/版本:
- README/DESIGN同步为Milkdown + v0.3.10
- 项目结构树/技术栈/快捷键表更新

验证: typecheck(仅7预存), lint✅, test 96/96, vite build✅

src/renderer/components/Sidebar/Sidebar.tsx

@@ -1,4 +1,4 @@
-import React, { useCallback, useMemo } from 'react'
+import React, { useCallback, useMemo, useEffect, useRef } from 'react'
 import { useTabStore } from '../../stores/tabStore'
 import { useSidebarStore } from '../../stores/sidebarStore'
 import { getFileName } from '../../lib/fileUtils'
@@ -8,6 +8,7 @@ import { FileTree } from '../FileTree'
 import { useSidebarResize } from '../../hooks/useSidebarResize'
 import { useFolderOperations } from '../../hooks/useFolderOperations'
 import { useAutoExpandDir } from '../../hooks/useAutoExpandDir'
+import { useActiveHeading } from '../../hooks/useActiveHeading'
 import { OutlinePanel, parseHeadings } from '../OutlinePanel'
 import type { Heading } from '../OutlinePanel'
 import { getEditorView, useEditorStore } from '../../stores/editorStore'
@@ -33,6 +34,7 @@ export const Sidebar = React.memo(function Sidebar() {
   const { sidebarRef, startResize } = useSidebarResize()
   const { handleOpenFolder } = useFolderOperations()
   const setLoading = useEditorStore(s => s.setLoading)
+  const viewMode = useEditorStore(s => s.viewMode)
   useAutoExpandDir(activeFilePath)
 
   // Parse headings from active tab content
@@ -41,6 +43,22 @@ export const Sidebar = React.memo(function Sidebar() {
     return parseHeadings(activeTab.content)
   }, [activeTab?.content])
 
+  // D4: 追踪预览面板中的活跃标题
+  const previewRef = useRef<HTMLElement | null>(null)
+  useEffect(() => {
+    // 仅在预览模式时获取 preview DOM 节点
+    if (viewMode === 'preview') {
+      previewRef.current = document.getElementById('preview')
+    } else {
+      previewRef.current = null
+    }
+  }, [viewMode])
+
+  const activeHeadingIndex = useActiveHeading(
+    viewMode === 'preview' ? previewRef : { current: null },
+    headings
+  )
+
   // Navigate to heading in ProseMirror document tree
   const handleHeadingNavigate = useCallback((heading: Heading, index: number) => {
     const view = getEditorView()
@@ -149,7 +167,7 @@ export const Sidebar = React.memo(function Sidebar() {
         <OutlinePanel
           headings={headings}
           onNavigate={handleHeadingNavigate}
-          activeHeadingIndex={null}
+          activeHeadingIndex={activeHeadingIndex}
         />
       </div>
       <div