Add the optional node id/source fields to the TS contract authority

Why: PR #25 added the fields to the Go UINode; ts/types.ts is the
single authority that make contracts mirrors into the frontend and UI
repos, so the fields must originate here or the sync reverts manual
mirror edits (CI build caught exactly that).

Evidence: Regenerated mirrors and combined make test run in the Dev
workspace after re-pinning.

Impact: Type-only additive change.

Refs: Core PR #25; Dev task feature/generative-ui-u2

ts/types.ts

@@ -184,6 +184,9 @@ export type UINodeType =
 
 export interface UINode {
   type: UINodeType;
+  /** Surface 层节点级标注（Generative UI U2）：整页唯一稳定 id 与事实来源标识，旧路径不填。 */
+  id?: string;
+  source?: string[];
   title?: string;
   items?: string[];
   kv?: [string, string][];