feat(p2.6): trust_drift_detector 接入 ai_slo_watchdog_job W-6

P2.6 接入 2026-04-24 ogt + Claude Sonnet 4.6

問題: trust_drift_detector.py 是孤立服務（零引用），Playbook 信任度
      偏態（盲目樂觀/學習鎖死）從未被任何監控機制感知

修復: ai_slo_watchdog_job._check_once() 新增 W-6 Trust Drift 檢查
  - 呼叫 get_trust_drift_detector().run()（偵測 + 寫 ai_governance_events）
  - 偵測到偏態時加入 violations 清單 → 觸發 TYPE-8M Meta-System 告警
  - checks 計數從 5 → 6

覆蓋案例:
  - optimism_bias: >70% Playbook trust_score >0.9 → PostExecutionVerifier 可能失效
  - confidence_collapse: >70% Playbook trust_score <0.3 → EWMA 計算/執行誤判

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

apps/api/src/jobs/ai_slo_watchdog_job.py

@@ -112,8 +112,26 @@ async def _check_once() -> None:
     except Exception as e:
         logger.warning("watchdog_w5_stuck_analysis_check_failed", error=str(e))
 
+    # W-6: Trust Drift 偵測（Playbook 信任度分布偏態）
+    # P2.6 接入 2026-04-24 ogt + Claude Sonnet 4.6
+    # trust_drift_detector 是孤立服務，此處首次接入 watchdog 自動觸發
+    try:
+        from src.services.trust_drift_detector import get_trust_drift_detector
+        dist = await get_trust_drift_detector().run()
+        if dist.drift_detected:
+            drift_labels = {
+                "optimism_bias": "盲目樂觀 — PostExecutionVerifier 可能失效或 RAG 資料污染",
+                "confidence_collapse": "學習鎖死 — EWMA 計算異常或所有執行誤判失敗",
+            }
+            label = drift_labels.get(dist.drift_type or "", dist.drift_type or "未知")
+            violations.append(
+                f"Trust Drift 偵測到 {label}（高分 {dist.high_ratio:.0%} / 低分 {dist.low_ratio:.0%}，共 {dist.total} 個 Playbook）"
+            )
+    except Exception as e:
+        logger.warning("watchdog_w6_trust_drift_check_failed", error=str(e))
+
     if not violations:
-        logger.debug("ai_slo_watchdog_all_ok", checks=5)
+        logger.debug("ai_slo_watchdog_all_ok", checks=6)
         return
 
     # 去重：violations 相同內容 1 小時內不重複發