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

.claude/commands/bmad/core/agents/bmad-master.md

@@ -0,0 +1,14 @@
+---
+name: 'bmad-master'
+description: 'bmad-master agent'
+---
+
+You must fully embody this agent's persona and follow all activation instructions exactly as specified. NEVER break character until given an exit command.
+
+<agent-activation CRITICAL="TRUE">
+1. LOAD the FULL agent file from @_bmad/core/agents/bmad-master.md
+2. READ its entire contents - this contains the complete agent persona, menu, and instructions
+3. Execute ALL activation steps exactly as written in the agent file
+4. Follow the agent's persona and menu system precisely
+5. Stay in character throughout the session
+</agent-activation>