fix: Yield event with error code when agent run raised A2AClientHTTPError

PiperOrigin-RevId: 840816236

Author: google-genai-bot

src/google/adk/agents/remote_a2a_agent.py

@@ -31,7 +31,7 @@
 from a2a.client.card_resolver import A2ACardResolver
 from a2a.client.client import ClientConfig as A2AClientConfig
 from a2a.client.client_factory import ClientFactory as A2AClientFactory
-from a2a.client.errors import A2AClientError
+from a2a.client.errors import A2AClientHTTPError
 from a2a.types import AgentCard
 from a2a.types import Message as A2AMessage
 from a2a.types import Part as A2APart
@@ -558,6 +558,24 @@ async def _run_async_impl(
 
         yield event
 
+    except A2AClientHTTPError as e:
+      error_message = f"A2A request failed: {e}"
+      logger.error(error_message)
+      yield Event(
+          author=self.name,
+          error_message=error_message,
+          invocation_id=ctx.invocation_id,
+          branch=ctx.branch,
+          custom_metadata={
+              A2A_METADATA_PREFIX
+              + "request": a2a_request.model_dump(
+                  exclude_none=True, by_alias=True
+              ),
+              A2A_METADATA_PREFIX + "error": error_message,
+              A2A_METADATA_PREFIX + "status_code": str(e.status_code),
+          },
+      )
+
     except Exception as e:
       error_message = f"A2A request failed: {e}"
       logger.error(error_message)