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/math-intrinsics/isInteger.d.ts

@@ -0,0 +1,3 @@
+declare function isInteger(argument: unknown): argument is number;
+
+export = isInteger;