fix(p0.4): Playbook 學習鏈三道修復 — partial index + race防護 + 手動路徑接線

ADR-092 P0.4 Playbook EWMA 學習閉環的 DB / Repository / Service 三層修補。

DB 層 (db-expert-fix by Engineer-B):
- ApprovalRecord.matched_playbook_id 移除 index=True，改 __table_args__ partial index
  (WHERE matched_playbook_id IS NOT NULL) — 多數列 NULL，full index 浪費空間
- adr092_p1_learning_chain_rollback.sql: 純 ROLLBACK SQL（DBA 手動執行）

Repository 層:
- playbook_repository.py: SELECT FOR UPDATE 防 lost update
  避免並發 EWMA 更新覆蓋彼此

Service 層 (P0.4 修復):
- proposal_service.py: 手動審核路徑補 _try_playbook_match_id 呼叫
  decision_manager auto_execute 路徑已有此邏輯（行 2035），
  此處補手動路徑缺口，使 matched_playbook_id 可寫入 DB → EWMA 才能演化

測試:
- test_playbook_repository_race_condition.py: 3 cases SELECT FOR UPDATE 防 race
  正確阻擋並發 EWMA 更新（pass）

Note: migration SQL 待 DBA 手動執行（feedback_dev_prod_separation.md），
      不執行 alembic upgrade（statu 文件禁忌條款）。

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

apps/api/src/services/proposal_service.py

@@ -246,6 +246,12 @@ class ProposalService:
                 metadata["signoz_correlation"] = llm_proposal.get("signoz_correlation", "")
                 metadata["optimization_suggestions"] = llm_proposal.get("optimization_suggestions", [])
 
+            # 2026-04-25 P0.4 修復 by Claude Engineer-B:
+            # 手動路徑（API 呼叫 generate_proposal）補 Playbook RAG 匹配，
+            # 讓 matched_playbook_id 得以寫入 DB，學習服務 EWMA 才能更新 trust score。
+            # decision_manager auto_execute 路徑已有此邏輯（行 2035），此處補手動路徑缺口。
+            matched_pb_id: str | None = await self._try_playbook_match_id(incident)
+
             approval_create = ApprovalRequestCreate(
                 action=action,
                 description=description,
@@ -255,6 +261,7 @@ class ProposalService:
                 requested_by="OpenClaw AI",
                 incident_id=incident_id,
                 metadata=metadata,
+                matched_playbook_id=matched_pb_id,
             )
 
             approval = await self._approval_service.create_approval(approval_create)
@@ -354,6 +361,55 @@ class ProposalService:
 
         return action_type, action, description
 
+    # =========================================================================
+    # 輔助方法: Playbook RAG 匹配（P0.4 2026-04-25 by Claude Engineer-B）
+    # =========================================================================
+
+    async def _try_playbook_match_id(self, incident: Incident) -> str | None:
+        """
+        嘗試 Playbook RAG 匹配，回傳 matched_playbook_id（相似度 >= 0.85 才填）。
+
+        設計動機：手動路徑（generate_proposal）補 matched_playbook_id，
+        讓學習服務 EWMA 能在人工審核後更新 Playbook trust score。
+        邏輯與 decision_manager._try_playbook_match 相同，但只回傳 ID 不改 action。
+        失敗時靜默返回 None（不阻塞主流程）。
+        """
+        PLAYBOOK_SIMILARITY_THRESHOLD = 0.85
+        try:
+            from src.models.playbook import SymptomPattern
+            from src.services.playbook_service import get_playbook_service
+
+            alert_names = [s.alert_name for s in incident.signals] if incident.signals else []
+            symptoms = SymptomPattern(
+                alert_names=alert_names,
+                affected_services=incident.affected_services or [],
+                severity_range=[incident.severity.value] if incident.severity else ["P2"],
+            )
+            recommendations = await get_playbook_service().get_recommendations(
+                symptoms=symptoms,
+                top_k=1,
+            )
+            if not recommendations:
+                return None
+            best_match = recommendations[0]
+            if best_match.similarity_score < PLAYBOOK_SIMILARITY_THRESHOLD:
+                return None
+            pb_id = best_match.playbook.playbook_id
+            logger.info(
+                "proposal_playbook_matched",
+                incident_id=incident.incident_id,
+                playbook_id=pb_id,
+                similarity=best_match.similarity_score,
+            )
+            return pb_id
+        except Exception as e:
+            logger.debug(
+                "proposal_playbook_match_skipped",
+                incident_id=getattr(incident, "incident_id", "?"),
+                error=str(e),
+            )
+            return None
+
     # =========================================================================
     # 輔助方法: 建立 BlastRadius
     # =========================================================================