build: raise langgraph recursion limit to 80

The default 25 was tripping on iterative builds (list -> write*3 -> test
-> deploy is already 12-18 steps; any retry blew the cap).

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

agent.py

@@ -114,6 +114,11 @@ class AgentBuilder(A2AAgent[BuilderConfig, NoAuth]):
             async for event in graph.astream_events(
                 {"messages": [{"role": "user", "content": user_msg}]},
                 version="v2",
+                # Default langgraph cap is 25 steps; one deepagents
+                # build (list → write*3 → test → deploy) easily uses
+                # 12-18, and any retry pushes it past the limit. Give
+                # the loop headroom without letting it run away.
+                config={"recursion_limit": 80},
             ):
                 kind = event.get("event")
                 tname = event.get("name") or ""