feat: add realtime subagent status report

frontend/src/core/threads/hooks.ts

@@ -1,4 +1,5 @@
 import type { HumanMessage } from "@langchain/core/messages";
+import type { AIMessage } from "@langchain/langgraph-sdk";
 import type { ThreadsClient } from "@langchain/langgraph-sdk/client";
 import { useStream, type UseStream } from "@langchain/langgraph-sdk/react";
 import { useMutation, useQuery, useQueryClient } from "@tanstack/react-query";
@@ -7,6 +8,7 @@ import { useCallback } from "react";
 import type { PromptInputMessage } from "@/components/ai-elements/prompt-input";
 
 import { getAPIClient } from "../api";
+import { useUpdateSubtask } from "../tasks/context";
 import { uploadFiles } from "../uploads";
 
 import type {
@@ -25,14 +27,28 @@ export function useThreadStream({
   onFinish?: (state: AgentThreadState) => void;
 }) {
   const queryClient = useQueryClient();
+  const updateSubtask = useUpdateSubtask();
   const thread = useStream<AgentThreadState>({
     client: getAPIClient(),
     assistantId: "lead_agent",
     threadId: isNewThread ? undefined : threadId,
     reconnectOnMount: true,
     fetchStateHistory: true,
-    onCustomEvent(event) {
+    onCustomEvent(event: unknown) {
       console.info(event);
+      if (
+        typeof event === "object" &&
+        event !== null &&
+        "type" in event &&
+        event.type === "task_running"
+      ) {
+        const e = event as {
+          type: "task_running";
+          task_id: string;
+          message: AIMessage;
+        };
+        updateSubtask({ id: e.task_id, latestMessage: e.message });
+      }
     },
     onFinish(state) {
       onFinish?.(state.values);