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/is-promise/index.js

@@ -0,0 +1,6 @@
+module.exports = isPromise;
+module.exports.default = isPromise;
+
+function isPromise(obj) {
+  return !!obj && (typeof obj === 'object' || typeof obj === 'function') && typeof obj.then === 'function';
+}