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

keep-notes/lib/types.ts

@@ -37,11 +37,17 @@ export interface Note {
   reminderRecurrence: string | null;
   reminderLocation: string | null;
   isMarkdown: boolean;
+  size: NoteSize;
   order: number;
   createdAt: Date;
   updatedAt: Date;
+  embedding?: number[] | null;
+  sharedWith?: string[];
+  userId?: string | null;
 }
 
+export type NoteSize = 'small' | 'medium' | 'large';
+
 export interface LabelWithColor {
   name: string;
   color: LabelColorName;
@@ -160,3 +166,11 @@ export const NOTE_COLORS = {
 } as const;
 
 export type NoteColor = keyof typeof NOTE_COLORS;
+
+/**
+ * Query types for adaptive search weighting
+ * - 'exact': User searched with quotes, looking for exact match (e.g., "Error 404")
+ * - 'conceptual': User is asking a question or looking for concepts (e.g., "how to cook")
+ * - 'mixed': No specific pattern detected, use default weights
+ */
+export type QueryType = 'exact' | 'conceptual' | 'mixed';