feat: rename file on save when title slug doesn't match filename

When Cmd+S is pressed, after saving content, checks if the note's
title slug differs from its current filename. If so, triggers
rename_note to update the file on disk, tabs, breadcrumbs, and
wikilinks. Adds needsRenameOnSave() utility with tests.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

src/App.tsx

@@ -17,7 +17,7 @@ import { WelcomeScreen } from './components/WelcomeScreen'
 import { useMcpStatus } from './hooks/useMcpStatus'
 import { useVaultLoader } from './hooks/useVaultLoader'
 import { useSettings } from './hooks/useSettings'
-import { useNoteActions } from './hooks/useNoteActions'
+import { useNoteActions, needsRenameOnSave } from './hooks/useNoteActions'
 import { useCommitFlow } from './hooks/useCommitFlow'
 import { useViewMode } from './hooks/useViewMode'
 import { useEntryActions } from './hooks/useEntryActions'
@@ -358,14 +358,25 @@ function App() {
     }
   }, [resolvedPath, vault.entries, notes, dialogs])
 
+  const handleRenameTab = useCallback(async (path: string, newTitle: string) => {
+    await savePendingForPath(path)
+    await notes.handleRenameNote(path, newTitle, resolvedPath, vault.replaceEntry).then(vault.loadModifiedFiles)
+  }, [notes, resolvedPath, vault, savePendingForPath])
+
   // Wrap handleSave to also persist unsaved notes that have no pending edits (user pressed Cmd+S without typing)
+  // and trigger file rename when the title slug doesn't match the filename.
   const handleSave = useCallback(async () => {
     const activeTab = notes.tabs.find(t => t.entry.path === notes.activeTabPath)
     const fallback = activeTab && vault.unsavedPaths.has(activeTab.entry.path)
       ? { path: activeTab.entry.path, content: activeTab.content }
       : undefined
     await handleSaveRaw(fallback)
-  }, [handleSaveRaw, notes.tabs, notes.activeTabPath, vault.unsavedPaths])
+
+    // After saving, check if filename needs to match the current title
+    if (activeTab && needsRenameOnSave(activeTab.entry.title, activeTab.entry.filename)) {
+      await handleRenameTab(activeTab.entry.path, activeTab.entry.title)
+    }
+  }, [handleSaveRaw, handleRenameTab, notes.tabs, notes.activeTabPath, vault.unsavedPaths])
 
   const commitFlow = useCommitFlow({ savePending, loadModifiedFiles: vault.loadModifiedFiles, commitAndPush: vault.commitAndPush, setToastMessage })
 
@@ -397,11 +408,6 @@ function App() {
     setToastMessage(`Type "${name}" created`)
   }, [notes])
 
-  const handleRenameTab = useCallback(async (path: string, newTitle: string) => {
-    await savePendingForPath(path)
-    await notes.handleRenameNote(path, newTitle, resolvedPath, vault.replaceEntry).then(vault.loadModifiedFiles)
-  }, [notes, resolvedPath, vault, savePendingForPath])
-
   /** H1→title sync: update VaultEntry.title and tab entry in memory. */
   const handleTitleSync = useCallback((path: string, newTitle: string) => {
     vault.updateEntry(path, { title: newTitle })

src/hooks/useNoteActions.test.ts

@@ -5,6 +5,7 @@ import { isTauri, mockInvoke } from '../mock-tauri'
 import type { VaultEntry } from '../types'
 import {
   slugify,
+  needsRenameOnSave,
   buildNewEntry,
   generateUntitledName,
   entryMatchesTarget,
@@ -94,6 +95,22 @@ describe('slugify', () => {
   })
 })
 
+describe('needsRenameOnSave', () => {
+  it('returns true when filename does not match title slug', () => {
+    expect(needsRenameOnSave('My New Note', 'untitled-note.md')).toBe(true)
+    expect(needsRenameOnSave('Run good ads for newsletter', 'untitled-note-9.md')).toBe(true)
+  })
+
+  it('returns false when filename matches title slug', () => {
+    expect(needsRenameOnSave('My Note', 'my-note.md')).toBe(false)
+    expect(needsRenameOnSave('Hello World', 'hello-world.md')).toBe(false)
+  })
+
+  it('returns false for untitled note with matching slug', () => {
+    expect(needsRenameOnSave('Untitled note', 'untitled-note.md')).toBe(false)
+  })
+})
+
 describe('buildNewEntry', () => {
   it('creates a VaultEntry with correct fields', () => {
     const entry = buildNewEntry({

src/hooks/useNoteActions.ts

@@ -104,6 +104,11 @@ export function slugify(text: string): string {
   return result || 'untitled'
 }
 
+/** Check if a note's filename doesn't match the slug of its current title. */
+export function needsRenameOnSave(title: string, filename: string): boolean {
+  return `${slugify(title)}.md` !== filename
+}
+
 /** Generate a unique "Untitled <type>" name by checking existing entries and pending names. */
 export function generateUntitledName(entries: VaultEntry[], type: string, pending?: Set<string>): string {
   const baseName = `Untitled ${type.toLowerCase()}`