fix: improve note interactions and markdown LaTeX support

## Bug Fixes

### Note Card Actions
- Fix broken size change functionality (missing state declaration)
- Implement React 19 useOptimistic for instant UI feedback
- Add startTransition for non-blocking updates
- Ensure smooth animations without page refresh
- All note actions now work: pin, archive, color, size, checklist

### Markdown LaTeX Rendering
- Add remark-math and rehype-katex plugins
- Support inline equations with dollar sign syntax
- Support block equations with double dollar sign syntax
- Import KaTeX CSS for proper styling
- Equations now render correctly instead of showing raw LaTeX

## Technical Details

- Replace undefined currentNote references with optimistic state
- Add optimistic updates before server actions for instant feedback
- Use router.refresh() in transitions for smart cache invalidation
- Install remark-math, rehype-katex, and katex packages

## Testing

- Build passes successfully with no TypeScript errors
- Dev server hot-reloads changes correctly

_bmad/_config/manifest.yaml

@@ -1,9 +1,11 @@
 installation:
   version: 6.0.0-alpha.22
-  installDate: 2026-01-06T17:15:56.602Z
-  lastUpdated: 2026-01-06T17:15:56.602Z
+  installDate: 2026-01-09T12:45:17.078Z
+  lastUpdated: 2026-01-09T12:45:17.078Z
 modules:
   - core
   - bmm
 ides:
   - gemini
+  - claude-code
+  - github-copilot