fix(agent): byte-cap recovery status line no longer claims HTTP 413

Review note (BearHuddleston, optional): 400 and status-less byte caps now reach
_recover_payload_too_large, so its status line drops the hardcoded '(413)'.

agent/turn_overflow.py

@@ -227,7 +227,7 @@ def _recover_payload_too_large(st: _Recovery, _retry: TurnRetryState) -> Overflo
     if exhausted is not None:
         return exhausted
     agent._buffer_diagnostic_status(
-        f"⚠️  Request payload too large (413) — compression attempt "
+        f"⚠️  Request payload too large — compression attempt "
         f"{st.compression_attempts}/{st.max_compression_attempts}..."
     )