Gateway: hide delegated threads unless they wait on the user

gateway/src/t3/types.ts

@@ -68,7 +68,9 @@ export interface ThreadShell {
   lastError?: string | null;
   modelSelection: ModelSelection;
   runtimeMode?: string;
-  lineage: { relationshipToParent: Open<"subagent"> | null };
+  lineage: { relationshipToParent: Open<"fork" | "subagent"> | null };
+  /** Set on threads an agent started with delegate_task, which T3 does not mark as subagents. */
+  delegatedFrom?: { environmentId: string; threadId: string; title: string };
   settledOverride?: Open<"settled"> | null;
 }