feat(messaging): OPS-005 이벤트 발행 연결 신뢰성 (BAT-047)

발행 전용 연결의 idle heartbeat 사망 후 첫 발행 유실 결함 제거.
- REQ-091 발행 재시도 + 강제 재연결(_force_reconnect, is_open 불신)
- REQ-092 idle keepalive(execution-loop 단일스레드 틱, process_data_events time_limit=0)
- REQ-093 DLQ 가시성 + emit 실패 ERROR 경보(구조화 로그, dcy-029 재사용)
- REQ-094 baseline 문서 정합(runtime-flows/operations/project-structure)

독립 opus QC PASS-WITH-NOTES → 시정 2건(ruff F401, AC-3 프로덕션 경로) 완료.
554 passed/47 skipped/회귀 0/ruff clean. NFR-1 wire 무회귀(interface-contract diff 0).
BAT-047 release-candidate, REQ-091~094 Implemented. dcy-031. M2 트랙B.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01VHtM5Ws1HKCKQ4JGi6GRb5

trex_core/application/messaging.py

@@ -112,6 +112,15 @@ class MessagingTransport(Protocol):
         exchange, dispatch to handler. Blocks until `stop` is set."""
         ...
 
+    def keepalive_tick(self) -> None:
+        """Process pending I/O frames to keep the connection alive (REQ-092).
+
+        MUST be called from the thread that owns this transport instance.
+        Non-blocking (time_limit=0 equivalent). Implementations that do not
+        need keepalive (e.g. InMemoryTransport) should be a no-op.
+        """
+        ...
+
     def health(self) -> TransportHealth:
         """Current connection state (REQ-024)."""
         ...