refactor: extract useConflictFlow, useAppSave, useVaultBridge from App.tsx

App.tsx was 702 lines and the highest-churn file (102 commits/month).
Extract three hooks to reduce it to 537 lines and distribute future
changes across focused modules:
- useConflictFlow: conflict resolution orchestration
- useAppSave: save/flush/rename orchestration
- useVaultBridge: agent/MCP file operation handlers

All files score 10.0 on CodeScene. 2226 tests pass.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

src/hooks/useAppSave.ts

@@ -0,0 +1,111 @@
+import { useCallback, useEffect, useRef } from 'react'
+import { useEditorSaveWithLinks } from './useEditorSaveWithLinks'
+import { needsRenameOnSave } from './useNoteRename'
+import { flushEditorContent } from '../utils/autoSave'
+import type { VaultEntry } from '../types'
+
+interface TabState {
+  entry: VaultEntry
+  content: string
+}
+
+function findUnsavedFallback(
+  tabs: TabState[], activeTabPath: string | null, unsavedPaths: Set<string>,
+): { path: string; content: string } | undefined {
+  const activeTab = tabs.find(t => t.entry.path === activeTabPath)
+  if (!activeTab || !unsavedPaths.has(activeTab.entry.path)) return undefined
+  return { path: activeTab.entry.path, content: activeTab.content }
+}
+
+function activeTabNeedsRename(tabs: TabState[], activeTabPath: string | null): { path: string; title: string } | null {
+  const activeTab = tabs.find(t => t.entry.path === activeTabPath)
+  if (!activeTab) return null
+  return needsRenameOnSave(activeTab.entry.title, activeTab.entry.filename)
+    ? { path: activeTab.entry.path, title: activeTab.entry.title }
+    : null
+}
+
+interface AppSaveDeps {
+  updateEntry: (path: string, patch: Partial<VaultEntry>) => void
+  setTabs: Parameters<typeof useEditorSaveWithLinks>[0]['setTabs']
+  setToastMessage: (msg: string | null) => void
+  loadModifiedFiles: () => void
+  clearUnsaved: (path: string) => void
+  unsavedPaths: Set<string>
+  tabs: TabState[]
+  activeTabPath: string | null
+  handleRenameNote: (path: string, newTitle: string, vaultPath: string, onEntryRenamed: (oldPath: string, newEntry: Partial<VaultEntry> & { path: string }, newContent: string) => void) => Promise<void>
+  replaceEntry: (oldPath: string, newEntry: Partial<VaultEntry> & { path: string }, newContent: string) => void
+  resolvedPath: string
+}
+
+export function useAppSave({
+  updateEntry, setTabs, setToastMessage,
+  loadModifiedFiles, clearUnsaved, unsavedPaths,
+  tabs, activeTabPath,
+  handleRenameNote, replaceEntry, resolvedPath,
+}: AppSaveDeps) {
+  const contentChangeRef = useRef<(path: string, content: string) => void>(() => {})
+
+  const onAfterSave = useCallback(() => {
+    loadModifiedFiles()
+  }, [loadModifiedFiles])
+
+  const onNotePersisted = useCallback((path: string) => {
+    clearUnsaved(path)
+  }, [clearUnsaved])
+
+  const { handleSave: handleSaveRaw, handleContentChange, savePendingForPath, savePending } = useEditorSaveWithLinks({
+    updateEntry, setTabs, setToastMessage, onAfterSave, onNotePersisted,
+  })
+
+  useEffect(() => { contentChangeRef.current = handleContentChange }, [handleContentChange])
+
+  // Refs for stable closure in flushBeforeAction
+  const tabsRef = useRef(tabs)
+  tabsRef.current = tabs // eslint-disable-line react-hooks/refs -- ref sync pattern
+  const unsavedPathsRef = useRef(unsavedPaths)
+  unsavedPathsRef.current = unsavedPaths // eslint-disable-line react-hooks/refs -- ref sync pattern
+
+  const flushBeforeAction = useCallback(async (path: string) => {
+    try {
+      await flushEditorContent(path, {
+        savePendingForPath,
+        getTabContent: (p) => tabsRef.current.find(t => t.entry.path === p)?.content,
+        isUnsaved: (p) => unsavedPathsRef.current.has(p),
+        onSaved: (p) => { clearUnsaved(p) },
+      })
+    } catch (err) {
+      setToastMessage(`Auto-save failed: ${err}`)
+      throw err
+    }
+  }, [savePendingForPath, clearUnsaved, setToastMessage])
+
+  const handleRenameTab = useCallback(async (path: string, newTitle: string) => {
+    await savePendingForPath(path)
+    await handleRenameNote(path, newTitle, resolvedPath, replaceEntry).then(loadModifiedFiles)
+  }, [handleRenameNote, resolvedPath, replaceEntry, savePendingForPath, loadModifiedFiles])
+
+  const handleSave = useCallback(async () => {
+    await handleSaveRaw(findUnsavedFallback(tabs, activeTabPath, unsavedPaths))
+    const rename = activeTabNeedsRename(tabs, activeTabPath)
+    if (rename) await handleRenameTab(rename.path, rename.title)
+  }, [handleSaveRaw, handleRenameTab, tabs, activeTabPath, unsavedPaths])
+
+  const handleTitleSync = useCallback((path: string, newTitle: string) => {
+    savePendingForPath(path)
+      .then(() => handleRenameNote(path, newTitle, resolvedPath, replaceEntry))
+      .then(loadModifiedFiles)
+      .catch((err) => console.error('Title rename failed:', err))
+  }, [handleRenameNote, resolvedPath, replaceEntry, savePendingForPath, loadModifiedFiles])
+
+  return {
+    contentChangeRef,
+    handleContentChange,
+    handleSave,
+    handleTitleSync,
+    savePending,
+    savePendingForPath,
+    flushBeforeAction,
+  }
+}