test: restore asyncio marker after rebase conflict resolution

During the #136 rebase onto latest main, conflict resolution in test_react_agent_gateway_injection.py dropped the @pytest.mark.asyncio decorator on test_react_agent_auto_compress_triggers_before_model_call.\n\nThis commit restores the decorator so pytest executes the async test correctly under the existing asyncio plugin configuration.\n\nVerification:\n- /Users/lang/workspace/github/Deterministic-Agent-Runtime-Engine/.venv/bin/pytest -q tests/unit/test_context_compression.py tests/unit/test_openai_model_adapter.py tests/unit/test_transport_adapters.py tests/unit/test_react_agent_gateway_injection.py\n- Result: 33 passed.

Author: mindfn

tests/unit/test_react_agent_gateway_injection.py

@@ -353,6 +353,8 @@ async def test_react_agent_emits_terminal_message_for_max_round_exit() -> None:
     assert getattr(last_envelope, "event_type", None) == TransportEventType.MESSAGE.value
     assert "达到最大轮次" in str(getattr(last_envelope, "payload", {}).get("resp", {}).get("output", ""))
 
+
+@pytest.mark.asyncio
 async def test_react_agent_auto_compress_triggers_before_model_call() -> None:
     context = _CompressionRecordingContext(config=Config())
     context.budget.max_tokens = 100