v0.3.6: 修复文档大纲导航Bug + 新增自动保存功能

Bug修复:
  - 文档大纲点击标题未定位到编辑器内容 (P0)
  - 根因: raw markdown字符偏移 ≠ ProseMirror文档位置
  - 改为通过 view.state.doc.descendants() 遍历节点树,
    按 heading类型名 + level + textContent 三重匹配定位

新增功能:
  - 自动保存 (2秒防抖), 仅对文件标签页生效
  - 状态栏显示 自动/保存中... 指示器

版本同步: package.json / AboutDialog / README 均更新至 v0.3.6

src/renderer/hooks/useAutoSave.ts

@@ -0,0 +1,87 @@
+import { useEffect, useRef, useState, useCallback } from 'react'
+import { useTabStore } from '../stores/tabStore'
+import { logError } from '../lib/errorHandler'
+
+/** Debounce delay for auto-save (ms) */
+const AUTO_SAVE_DELAY = 2000
+
+/**
+ * Auto-save hook: subscribes to Zustand tab store, debounces content changes
+ * and saves automatically after a pause in editing for file-backed tabs.
+ *
+ * Uses `useTabStore.getState()` and `.subscribe()` so it doesn't need to
+ * re-render on every keystroke — the effect is triggered once and runs
+ * reactively via the store subscription.
+ */
+export function useAutoSave(): { isAutoSaving: boolean; autoSaveEnabled: boolean; toggleAutoSave: () => void } {
+  const [isAutoSaving, setIsAutoSaving] = useState(false)
+  const [autoSaveEnabled, setAutoSaveEnabled] = useState(true)
+  const timerRef = useRef<ReturnType<typeof setTimeout> | null>(null)
+  const isSavingRef = useRef(false)
+  const enabledRef = useRef(true)
+
+  const toggleAutoSave = useCallback(() => {
+    setAutoSaveEnabled(prev => {
+      const next = !prev
+      enabledRef.current = next
+      if (!next && timerRef.current) {
+        clearTimeout(timerRef.current)
+        timerRef.current = null
+      }
+      return next
+    })
+  }, [])
+
+  useEffect(() => {
+    // Subscribe to Zustand store — fires on every state change
+    const unsub = useTabStore.subscribe((state) => {
+      if (!enabledRef.current) return
+
+      const tab = state.getActiveTab()
+      if (!tab || !tab.filePath || !tab.isModified) return
+
+      // Debounce: clear previous timer, start new one
+      if (timerRef.current) {
+        clearTimeout(timerRef.current)
+      }
+
+      timerRef.current = setTimeout(async () => {
+        if (isSavingRef.current) return
+
+        // Re-read latest state inside the timeout callback
+        const currentState = useTabStore.getState()
+        const currentTab = currentState.getActiveTab()
+        if (!currentTab || !currentTab.filePath || !currentTab.isModified) return
+
+        isSavingRef.current = true
+        setIsAutoSaving(true)
+
+        try {
+          if (!window.electronAPI) return
+          const result = await window.electronAPI.saveFile({
+            filePath: currentTab.filePath,
+            content: currentTab.content
+          })
+          if (result.success) {
+            currentState.setModified(currentTab.id, false)
+          }
+        } catch (error) {
+          logError('自动保存失败', error)
+        } finally {
+          setIsAutoSaving(false)
+          isSavingRef.current = false
+        }
+      }, AUTO_SAVE_DELAY)
+    })
+
+    return () => {
+      unsub()
+      if (timerRef.current) {
+        clearTimeout(timerRef.current)
+        timerRef.current = null
+      }
+    }
+  }, [])
+
+  return { isAutoSaving, autoSaveEnabled, toggleAutoSave }
+}