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/ajv/dist/vocabularies/jtd/nullable.d.ts

@@ -0,0 +1,4 @@
+import type { KeywordCxt } from "../../compile/validate";
+import { Code, Name } from "../../compile/codegen";
+export declare function checkNullable({ gen, data, parentSchema }: KeywordCxt, cond?: Code): [Name, Code];
+export declare function checkNullableObject(cxt: KeywordCxt, cond: Code): [Name, Code];