feat: revision graph improvements with multi-select and better branch ordering
- Add multi-select support with checkboxes for revision graph
- Improve collapsed stack UI with stacked card animation
- Add ast-grep rules (migrate from .grit files)
- Add no-direct-tauri-mutations lint rule
- Add livestore Tauri adapter and sync infrastructure
- Refactor db.ts to use collections with prefetching
- Add checkbox UI component
- Improve browser-only mocks for dev mode
- Various UI polish and cleanup