- Replace editable intro note with a static read-only WelcomeView component
- Add "使用指南" sidebar nav item always pointing to WelcomeView
- Fix React StrictMode double-seed race condition via module-level Promise singleton
- Add deduplicateDB() to clean up already-inserted duplicates on startup
- Add star button in editor title bar and sidebar note hover row
- Add visible delete button on note item hover in sidebar
- Default activeNoteId to '__welcome__' sentinel; deleted notes return to WelcomeView
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
