fix: Add debounced Undo/Redo system to avoid character-by-character history

- Add debounced state updates for title and content (500ms delay)
- Immediate UI updates with delayed history saving
- Prevent one-letter-per-undo issue
- Add cleanup for debounce timers on unmount

mcp-server/node_modules/fast-deep-equal/index.d.ts

@@ -0,0 +1,4 @@
+declare module 'fast-deep-equal' {
+    const equal: (a: any, b: any) => boolean;
+    export = equal;
+}