feat(ai): enforce single-writer automation router

apps/api/src/services/failure_watcher.py

@@ -216,44 +216,27 @@ class FailureWatcherService(IFailureWatcher):
             result["risk_level"] = "MEDIUM"
 
         if risk_level != "CRITICAL" and RISK_LEVELS.get(risk_level, {}).get("auto_repair"):
-            # 自動修復 (Phase 18.3: 傳入完整 failure_data)
-            success, repair_result = await self.execute_auto_repair(
+            # Executor failures must not recursively invoke a second writer.
+            # Queue the repair context for the controlled broker path instead.
+            await self._queue_ai_repair_followup(
                 audit_log_id=audit_log_id,
-                repair_strategy=analysis["suggested_repair"],
-                failure_data=failure_data,
+                analysis=analysis,
+                reason=(
+                    "executor failure routed to single-writer retry/repair queue; "
+                    "a new check-mode receipt is required before apply"
+                ),
             )
-            result["repair_attempted"] = True
-            result["repair_result"] = repair_result
-            result["next_action"] = "auto_repaired" if success else "escalate"
+            result["repair_attempted"] = False
+            result["repair_result"] = "single_writer_retry_or_repair_queued"
+            result["next_action"] = "ai_retry_queued"
 
             # 更新 AuditLog
             await self._update_audit_log_classification(
                 audit_log_id=audit_log_id,
                 classification=analysis["classification"],
-                auto_repair_attempted=True,
-                auto_repair_result=repair_result,
+                auto_repair_attempted=False,
+                auto_repair_result="single_writer_retry_or_repair_queued",
             )
-
-            if success:
-                # P0-1 補充: 記錄全域修復動作 (ADR-040)
-                from src.services.global_repair_cooldown import record_global_repair_action
-                await record_global_repair_action()
-
-                # 推送揭露通知 (自動修復成功)
-                await self._push_repair_notification(
-                    audit_log_id=audit_log_id,
-                    repair_result=repair_result,
-                    auto=True,
-                )
-            else:
-                # 失敗後排入 AI controlled retry / rollback，不再直接轉人工。
-                result["risk_level"] = "MEDIUM"
-                await self._queue_ai_repair_followup(
-                    audit_log_id=audit_log_id,
-                    analysis=analysis,
-                    reason="AI 受控自動修復失敗，已排入 rollback / transport / PlayBook 修復重試",
-                )
-                result["next_action"] = "ai_retry_queued"
         else:
             # CRITICAL: break-glass / hard blocker，不執行寫入。
             await self._queue_ai_repair_followup(
@@ -322,6 +305,18 @@ class FailureWatcherService(IFailureWatcher):
         audit_log_id: str,
         repair_strategy: str,
         failure_data: dict | None = None,
+    ) -> tuple[bool, str]:
+        """Fail closed when legacy code tries to bypass the single writer."""
+
+        raise RuntimeError(
+            "failure_watcher_direct_execution_disabled_use_single_writer_broker"
+        )
+
+    async def _legacy_execute_auto_repair_disabled(
+        self,
+        audit_log_id: str,
+        repair_strategy: str,
+        failure_data: dict | None = None,
     ) -> tuple[bool, str]:
         """
         執行自動修復 (僅限 LOW 風險)