[taskboard] add completion sync APIs

lib/types.ts

@@ -27,6 +27,9 @@ export type TaskRecord = {
   preferred_agent: string | null;
   reasoning_effort: string | null;
   model_hint: string | null;
+  result_summary: string | null;
+  result_detail: string | null;
+  completed_by: string | null;
   priority: TaskPriority;
   status: TaskStatus;
   tags: string[];
@@ -78,6 +81,15 @@ export type TaskEvent = {
   created_at: string;
 };
 
+export type TaskCallbackPayload = {
+  status?: TaskStatus;
+  dispatch_state?: DispatchState;
+  summary?: string | null;
+  detail?: string | null;
+  completed_by?: string | null;
+  last_error?: string | null;
+};
+
 export type WikiPageSummary = {
   filename: string;
   title: string;