- 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>