fix(api): 修復 Y/n 404 + 停用 Multi-Sig

1. proposal_service._load_incident() 改用 incident_service.get_from_working_memory()
   - brain engine 使用 awoooi:incidents: prefix，資料實際在 incident: prefix
   - 兩個 prefix 不符導致永遠 404 (Y/n 按鈕全部失敗)
   - 2026-04-02 ogt

2. trust_engine CRITICAL required_signatures 2→1
   - 統帥決策: 所有審核只需 1 層簽核
   - 2026-04-02 ogt

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

apps/api/src/core/trust_engine.py

@@ -71,7 +71,7 @@ LOW_KEYWORDS = [
 SIGNATURE_REQUIREMENTS: dict[RiskLevel, int] = {
     RiskLevel.LOW: 0,       # 自動放行
     RiskLevel.MEDIUM: 1,    # 單人簽核
-    RiskLevel.CRITICAL: 2,  # Multi-Sig 雙重簽核
+    RiskLevel.CRITICAL: 1,  # 2026-04-02 ogt: 統帥決策 — 只需 1 層審核，Multi-Sig 停用
 }
 
 

apps/api/src/services/proposal_service.py

@@ -42,6 +42,7 @@ from src.models.incident import (
 from src.services.approval_db import get_approval_service
 from src.services.incident_engine import get_incident_engine
 from src.services.incident_memory import get_incident_memory
+from src.services.incident_service import get_incident_service
 from src.services.openclaw import get_openclaw
 from src.services.trust_engine import normalize_action_pattern, trust_engine
 from src.utils.incident_converter import local_to_brain
@@ -291,14 +292,14 @@ class ProposalService:
 
     async def _load_incident(self, incident_id: str) -> Incident | None:
         """
-        載入 Incident (委派給 IncidentEngineAdapter)
+        載入 Incident (從 Working Memory 讀取)
 
-        ADR-046 (2026-04-01 ogt): 透過 IncidentEngineAdapter.get_incident()
-        取得 LocalIncident，key prefix 正確性由 brain DualIncidentMemory 保證
-        (awoooi:incidents:{id})，不再直接存取 Redis。
+        2026-04-02 ogt: 修復 brain engine 使用 awoooi:incidents: prefix
+        但資料實際儲存在 incident: prefix，導致永遠 404。
+        改用 incident_service.get_from_working_memory() 讀正確 key。
         """
         try:
-            return await get_incident_engine().get_incident(incident_id)
+            return await get_incident_service().get_from_working_memory(incident_id)
         except Exception as e:
             logger.warning(
                 "load_incident_failed",