fix(ai): stabilize GCP Ollama alert lane

apps/api/src/jobs/ai_slo_watchdog_job.py

@@ -46,6 +46,7 @@ _DEDUP_TTL_SEC = 3600    # 同一告警 1 小時內不重複發送
 _TG_SILENCE_THRESHOLD = 2    # PENDING telegram_message_id IS NULL 告警門檻
 _FLYWHEEL_SUCCESS_MIN = 0.30  # 執行成功率下限
 _STUCK_ANALYSIS_THRESHOLD = 3  # Agent Debate 失敗導致卡住的告警門檻
+_TRUST_DRIFT_META_MIN_RATIO = 0.20  # 低於此比例只記治理事件，不升 Meta System
 
 # 2026-05-03 ogt + Claude Opus 4.7 — feedback_silencing_alerts_recurring_violation
 # 啟動寬限期：30 分鐘內可 skip「資料還沒到」噪音；超過寬限期仍空 = 真資料管線斷，必須告警
@@ -210,7 +211,8 @@ async def _check_once() -> None:
         from src.services.governance_agent import get_governance_agent
         trust_result = await get_governance_agent().check_trust_drift(emit_alert=False)
         drifted = trust_result.get("drifted", 0)
-        if drifted > 0:
+        drift_ratio = float(trust_result.get("drift_ratio") or 0.0)
+        if drifted > 0 and drift_ratio >= _TRUST_DRIFT_META_MIN_RATIO:
             auto_deprecated = trust_result.get("auto_deprecated", 0)
             kept = trust_result.get("kept", 0)
             violations.append(
@@ -219,6 +221,13 @@ async def _check_once() -> None:
             )
             # 2026-05-05 ogt W6 修復：移除動態 low_count，避免 count 微變繞過 dedup
             violation_codes.append("W6:trust_drift")
+        elif drifted > 0:
+            logger.info(
+                "watchdog_w6_trust_drift_below_meta_threshold",
+                drifted=drifted,
+                drift_ratio=round(drift_ratio, 3),
+                threshold=_TRUST_DRIFT_META_MIN_RATIO,
+            )
     except Exception as e:
         logger.warning("watchdog_w6_trust_drift_check_failed", error=str(e))