fix: prevent crash in handleCreateNoteImmediate — slugify fallback + try/catch

- slugify now returns 'untitled' instead of empty string when input has only
  special characters, preventing invalid paths like '/vault//note.md'
- handleCreateNoteImmediate wrapped in try/catch — worst case shows a toast
  error instead of crashing the app
- Added Rust test for deeply nested directory creation in save_note_content
- Regression tests for slugify edge cases and handleCreateNoteImmediate with
  special-character types

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

src-tauri/src/vault/mod.rs

@@ -1261,6 +1261,17 @@ References:
         assert_eq!(fs::read_to_string(&path).unwrap(), content);
     }
 
+    #[test]
+    fn test_save_note_content_deeply_nested_new_directory() {
+        let dir = TempDir::new().unwrap();
+        let path = dir.path().join("a/b/c/deep-note.md");
+        let content = "---\ntitle: Deep\n---\n";
+
+        save_note_content(path.to_str().unwrap(), content).unwrap();
+        assert!(path.exists());
+        assert_eq!(fs::read_to_string(&path).unwrap(), content);
+    }
+
     // --- sidebar_label tests ---
 
     #[test]

src/hooks/useNoteActions.test.ts

@@ -77,13 +77,21 @@ describe('slugify', () => {
     expect(slugify('--hello--')).toBe('hello')
   })
 
-  it('handles empty string', () => {
-    expect(slugify('')).toBe('')
+  it('handles empty string with fallback', () => {
+    expect(slugify('')).toBe('untitled')
   })
 
   it('collapses multiple separators into one hyphen', () => {
     expect(slugify('hello   world---foo')).toBe('hello-world-foo')
   })
+
+  it('returns fallback for strings with only special characters', () => {
+    // slugify('+++') should not return empty string — it causes invalid paths
+    expect(slugify('+++')).not.toBe('')
+    expect(slugify('!!!')).not.toBe('')
+    expect(slugify('---')).not.toBe('')
+    expect(slugify('@#$')).not.toBe('')
+  })
 })
 
 describe('buildNewEntry', () => {
@@ -270,6 +278,20 @@ describe('resolveNewNote', () => {
     expect(entry.path).toBe('/other/vault/note/test.md')
     expect(entry.path).not.toContain('/Users/luca/Laputa')
   })
+
+  it('produces a valid path for custom types with special characters', () => {
+    const { entry } = resolveNewNote('My Note', 'Q&A', '/vault')
+    expect(entry.path).not.toContain('//')
+    expect(entry.path).toMatch(/\.md$/)
+    expect(entry.filename).not.toBe('.md')
+  })
+
+  it('produces a valid path when type is all special characters', () => {
+    const { entry } = resolveNewNote('My Note', '+++', '/vault')
+    // folder should not be empty, path should not have double slashes
+    expect(entry.path).not.toContain('//')
+    expect(entry.path).toMatch(/\.md$/)
+  })
 })
 
 describe('resolveNewType', () => {
@@ -612,6 +634,34 @@ describe('useNoteActions hook', () => {
     expect(tabContent).toContain('## Steps')
   })
 
+  it('handleCreateNoteImmediate does not throw for custom types with special characters', () => {
+    const { result } = renderHook(() => useNoteActions(makeConfig()))
+
+    expect(() => {
+      act(() => {
+        result.current.handleCreateNoteImmediate('Q&A')
+      })
+    }).not.toThrow()
+
+    const [entry] = addEntry.mock.calls[0]
+    expect(entry.isA).toBe('Q&A')
+    expect(entry.path).not.toContain('//')
+  })
+
+  it('handleCreateNoteImmediate does not throw for types that slugify to empty string', () => {
+    const { result } = renderHook(() => useNoteActions(makeConfig()))
+
+    expect(() => {
+      act(() => {
+        result.current.handleCreateNoteImmediate('+++')
+      })
+    }).not.toThrow()
+
+    const [entry] = addEntry.mock.calls[0]
+    expect(entry.path).not.toContain('//')
+    expect(entry.filename).not.toBe('.md')
+  })
+
   it('handleCreateNoteImmediate uses template for typed notes', () => {
     const typeEntry = makeEntry({ isA: 'Type', title: 'Project', template: '## Custom Template\n\n' })
     const { result } = renderHook(() => useNoteActions(makeConfig([typeEntry])))

src/hooks/useNoteActions.ts

@@ -100,7 +100,8 @@ export function buildNewEntry({ path, slug, title, type, status }: NewEntryParam
 }
 
 export function slugify(text: string): string {
-  return text.toLowerCase().replace(/[^a-z0-9]+/g, '-').replace(/(^-|-$)/g, '')
+  const result = text.toLowerCase().replace(/[^a-z0-9]+/g, '-').replace(/(^-|-$)/g, '')
+  return result || 'untitled'
 }
 
 /** Generate a unique "Untitled <type>" name by checking existing entries and pending names. */
@@ -392,17 +393,22 @@ export function useNoteActions(config: NoteActionsConfig) {
   }, [entries, persistNew, config.vaultPath])
 
   const handleCreateNoteImmediate = useCallback((type?: string) => {
-    const noteType = type || 'Note'
-    const title = generateUntitledName(entries, noteType, pendingNamesRef.current)
-    pendingNamesRef.current.add(title)
-    const template = resolveTemplate(entries, noteType)
-    const resolved = resolveNewNote(title, noteType, config.vaultPath, template)
-    openTabWithContent(resolved.entry, resolved.content)
-    addEntryWithMock(resolved.entry, resolved.content, addEntry)
-    config.trackUnsaved?.(resolved.entry.path)
-    config.markContentPending?.(resolved.entry.path, resolved.content)
-    signalFocusEditor({ selectTitle: true })
-    setTimeout(() => pendingNamesRef.current.delete(title), 500)
+    try {
+      const noteType = type || 'Note'
+      const title = generateUntitledName(entries, noteType, pendingNamesRef.current)
+      pendingNamesRef.current.add(title)
+      const template = resolveTemplate(entries, noteType)
+      const resolved = resolveNewNote(title, noteType, config.vaultPath, template)
+      openTabWithContent(resolved.entry, resolved.content)
+      addEntryWithMock(resolved.entry, resolved.content, addEntry)
+      config.trackUnsaved?.(resolved.entry.path)
+      config.markContentPending?.(resolved.entry.path, resolved.content)
+      signalFocusEditor({ selectTitle: true })
+      setTimeout(() => pendingNamesRef.current.delete(title), 500)
+    } catch (err) {
+      console.error('Failed to create note:', err)
+      setToastMessage('Failed to create note')
+    }
   }, [entries, openTabWithContent, addEntry, config.vaultPath, config.trackUnsaved, config.markContentPending]) // eslint-disable-line react-hooks/exhaustive-deps -- config callbacks are stable
 
   /** Close tab and discard entry+unsaved state if the note was never persisted. */