fix(gateway): propagate response_transformed flag through run_sync return dict

run_sync() cherry-picks fields from the run_conversation result dict into
a new response dict for the gateway. response_transformed was missing from
the cherry-pick list, so the gateway always saw it as False and suppressed
the final send even though a transform_llm_output hook had modified the content.

gateway/run.py

@@ -17041,6 +17041,7 @@ class GatewayRunner:
                 "context_length": _context_length,
                 "session_id": effective_session_id,
                 "response_previewed": result.get("response_previewed", False),
+                "response_transformed": result.get("response_transformed", False),
             }
         
         # Start progress message sender if enabled