fix: align agent-builder with longer pack timeouts

agent.py

@@ -17,8 +17,10 @@ because it needs three things forwarded from the caller:
 """
 from __future__ import annotations
 
+import asyncio
 import json
 import re
+from contextlib import suppress
 from typing import Any
 
 from pydantic import BaseModel
@@ -65,6 +67,7 @@ class AgentBuilder(A2AAgent[BuilderConfig, NoAuth]):
             "should do. Returns the live URL when ready."
         ),
         tags=["builder", "scaffold", "deepagents", "meta"],
+        stream=True,
     )
     async def build(
         self,
@@ -127,6 +130,13 @@ class AgentBuilder(A2AAgent[BuilderConfig, NoAuth]):
         final_state: dict[str, Any] = {}
         deployed_url: str | None = None
         last_reply: str = ""
+
+        async def _heartbeat() -> None:
+            while True:
+                await asyncio.sleep(20)
+                await ctx.emit_progress(f"agent-builder still working on {name!r}")
+
+        heartbeat_task = asyncio.create_task(_heartbeat())
         try:
             async for event in graph.astream_events(
                 {"messages": [{"role": "user", "content": user_msg}]},
@@ -156,6 +166,10 @@ class AgentBuilder(A2AAgent[BuilderConfig, NoAuth]):
                         final_state = out
         except Exception as exc:  # noqa: BLE001
             return {"error": f"build graph failed: {type(exc).__name__}: {exc}"}
+        finally:
+            heartbeat_task.cancel()
+            with suppress(asyncio.CancelledError):
+                await heartbeat_task
 
         for msg in final_state.get("messages") or []:
             content = msg.get("content") if isinstance(msg, dict) else getattr(msg, "content", None)