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/isNaN.js

@@ -0,0 +1,6 @@
+'use strict';
+
+/** @type {import('./isNaN')} */
+module.exports = Number.isNaN || function isNaN(a) {
+	return a !== a;
+};