fix(cma): 隔离扫尾 — kpi_alert_higher_better 拆账套 + tenant/switch 审计收口

任务 dama-entity-isolation-sweep-20260923（DAMA 独立回查漏项 / 任总 2026-09-23「按照建议执行」）

① 补漏同源全局键 kpi_alert_higher_better（system_configs，零 DDL）
   - deviation_engine: 新增 higher_better_key(entity_id)；get_higher_better_codes(db, entity_id)
     改为只读本账套键、不回退旧全局键；未配置 → DEFAULT_HIGHER_BETTER（兜底，与原行为逐字一致）
   - budget.py: GET/PUT /alert-direction 挂 get_entity_id，只读写会话账套键；body entity_id 不信
   - scripts/migrate_higher_better_key_entity_20260923.py: --check/--apply/--down + 库名保护 + 幂等
   - 生产实况：库内该键 0 行 ⇒ 无原值可搬运（--apply 走 skip 零写入），e1 行为不变

② kpi_visibility 口径裁定：角色级天然全局 = 非账套维度，不拆（关闭本项）
   - auth_middleware 注释 + docstring 登记「有意不做账套后缀」；口径字典
     docs/global-config-keys-caliber-20260923.md（含 budget_mode/budget_driver_mode 评估结论）

③ tenant/switch 审计收口
   - detail 显式 from_entity_id → to_entity_id + source + operator{id,username,name,role}
   - 审计失败不静默：同事务回滚 + AUDIT_WRITE_FAILED ERROR + HTTP 500（不留「改了但没审计」）
   - GET /current 无写路径不落审计；历史缺口不补写

证据：新增/改写用例 17 条；全量 1397 passed（去新增文件 1380 + 17）；RED 态 8 failed

backend/app/api/budget.py

@@ -1079,17 +1079,24 @@ def get_deviation_alert_attribution(
 @router.get("/alert-direction")
 def get_alert_direction(
     db: Session = Depends(get_db),
+    entity_id: int = Depends(get_entity_id),
 ):
-    """越高越好型KPI方向配置 (P2-⑤ 2026-08-28: system_configs 可维护)"""
-    from app.utils.deviation_engine import get_higher_better_codes, CONFIG_KEY_HIGHER_BETTER
+    """越高越好型KPI方向配置（**按会话账套**；2026-09-23 拆账套，零 DDL）
+
+    与 B1 `cash.current_balance` 同款：只读本账套键 `kpi_alert_higher_better.<entity_id>`，
+    本账套未配置 → 走 deviation_engine 内置默认表（兜底，不跨账套借用）。
+    """
+    from app.utils.deviation_engine import get_higher_better_codes, higher_better_key
     from app.models import SystemConfig
 
+    key = higher_better_key(entity_id)
     cfg = db.query(SystemConfig).filter(
-        SystemConfig.config_key == CONFIG_KEY_HIGHER_BETTER
+        SystemConfig.config_key == key
     ).first()
-    codes = get_higher_better_codes(db)
+    codes = get_higher_better_codes(db, entity_id)
     return {
-        "config_key": CONFIG_KEY_HIGHER_BETTER,
+        "config_key": key,
+        "entity_id": entity_id,
         "codes": codes,
         "is_configured": bool(cfg and cfg.config_value),
     }
@@ -1100,10 +1107,15 @@ def update_alert_direction(
     data: dict,
     db: Session = Depends(get_db),
     current_user=Depends(require_auth),
+    entity_id: int = Depends(get_entity_id),
 ):
-    """维护越高越好型KPI方向配置 (P2-⑤) body: {codes: ["SALES_TOTAL", ...]}"""
+    """维护越高越好型KPI方向配置 (P2-⑤) body: {codes: ["SALES_TOTAL", ...]}
+
+    账套隔离（2026-09-23）：只写本账套键 `kpi_alert_higher_better.<entity_id>`；
+    body 里的 `entity_id` 一律不信（会话账套为准，同 B1 口径）。
+    """
     import json as _json
-    from app.utils.deviation_engine import CONFIG_KEY_HIGHER_BETTER
+    from app.utils.deviation_engine import higher_better_key
     from app.models import SystemConfig
 
     codes = data.get("codes")
@@ -1111,19 +1123,20 @@ def update_alert_direction(
         raise HTTPException(400, "codes 必须是非空数组")
     codes = [str(c) for c in codes]
 
+    key = higher_better_key(entity_id)
     cfg = db.query(SystemConfig).filter(
-        SystemConfig.config_key == CONFIG_KEY_HIGHER_BETTER
+        SystemConfig.config_key == key
     ).first()
     if cfg:
         cfg.config_value = _json.dumps(codes, ensure_ascii=False)
     else:
         db.add(SystemConfig(
-            config_key=CONFIG_KEY_HIGHER_BETTER,
+            config_key=key,
             config_value=_json.dumps(codes, ensure_ascii=False),
-            description="越高越好型KPI编码列表（实际低于预算才告警）",
+            description=f"越高越好型KPI编码列表（实际低于预算才告警）— 账套 {int(entity_id)}",
         ))
     db.commit()
-    return {"success": True, "config_key": CONFIG_KEY_HIGHER_BETTER, "codes": codes}
+    return {"success": True, "config_key": key, "entity_id": entity_id, "codes": codes}
 
 
 @router.put("/deviation-alerts/{alert_id}")

backend/app/api/tenant.py

@@ -24,6 +24,15 @@
      无 `entity_id` 列，无需 DDL）。两字面**刻意不合并**：一个改「用户自己的会话账套」、
      一个改「平台全局状态记录」，合并后审计上不可分辨。口径登记见
      `docs/audit-and-notification-caliber-20260922.md`。
+  7. **审计缺口的收口（2026-09-23 dama-entity-isolation-sweep-20260923 §二）**：
+     - `detail` 显式给出 `from_entity_id → to_entity_id`（原先只有 `previous` 整包，
+       要人肉解析才知道「从哪来」）+ `source` + `operator`（id/username/role）。
+     - **审计失败不静默**：状态键与审计行走**同一事务**，审计写入异常 → `rollback()`
+       （状态变更一并回滚，绝不留「改了但没审计」的窗口）+ `logger.error(AUDIT_WRITE_FAILED…)`
+       + HTTP 500。日志前缀 `AUDIT_WRITE_FAILED` 供运维 grep/告警链订阅。
+     - `GET /current` **无写路径**（纯只读，且已限 it/ceo），故不落审计——不给读操作
+       写审计表，避免审计面被读流量稀释。
+     - 历史缺口（2026-09-22 止血操作无审计行）**不补写**：审计不得事后伪造。
 """
 from fastapi import APIRouter, Depends, HTTPException
 from pydantic import BaseModel
@@ -32,6 +41,10 @@ from app.database import get_db
 from app.auth_middleware import require_auth_401, require_role
 from app.models import SystemConfig, Entity, OperationLog
 
+import logging
+
+logger = logging.getLogger("cma.tenant")
+
 # 用户端点：统一要求会话 Bearer 鉴权（cma-api-auth-surface-audit-20260914）
 # 缺口：本 router 原无鉴权——无 token 可读当前租户、并可 POST /switch 改写
 # system_config.current_tenant（状态改写面）。收口为 require_auth_401。
@@ -82,11 +95,14 @@ def switch_tenant(data: TenantSwitchRequest, db: Session = Depends(get_db),
         raise HTTPException(404, "企业不存在")
 
     import json
+    from_entity_id = None
     previous = None
     cfg = db.query(SystemConfig).filter(SystemConfig.config_key == TENANT_KEY).first()
     if cfg and cfg.config_value:
         try:
             previous = json.loads(cfg.config_value)
+            if isinstance(previous, dict):
+                from_entity_id = previous.get("entity_id")
         except Exception:
             previous = None
 
@@ -112,19 +128,41 @@ def switch_tenant(data: TenantSwitchRequest, db: Session = Depends(get_db),
     # 2026-09-22 DAMA 回查 §4b 后补：user_id 记操作人（原 None ⇒ 无法追人）；
     # target_type/target_id 与 /auth/switch-entity 的 switch_entity 对齐 ⇒ 按账套可过滤
     # （operation_logs 无 entity_id 列，无须 DDL）。
-    db.add(OperationLog(
-        user_id=user.id,
-        action="switch_tenant_state",
-        target_type="entity",
-        target_id=data.entity_id,
-        detail={
-            "entity_id": data.entity_id,
-            "entity_name": ent.name,
-            "source": data.source,
-            "previous": previous,
-            "note": "current_tenant 状态记录变更（非数据维度）",
+    # 2026-09-23 收口：detail 显式 from→to / source / operator；审计失败不静默（见 §7）。
+    audit_detail = {
+        "from_entity_id": from_entity_id,
+        "to_entity_id": data.entity_id,
+        "entity_id": data.entity_id,          # 兼容既有消费方/用例（= to）
+        "entity_name": ent.name,
+        "source": data.source,
+        "operator": {
+            "user_id": user.id,
+            "username": getattr(user, "username", None),
+            "name": getattr(user, "name", None),
+            "role": getattr(user, "role", None),
         },
-    ))
-    db.commit()
+        "previous": previous,
+        "note": "current_tenant 状态记录变更（非数据维度）",
+    }
+    try:
+        db.add(OperationLog(
+            user_id=user.id,
+            action="switch_tenant_state",
+            target_type="entity",
+            target_id=data.entity_id,
+            detail=audit_detail,
+        ))
+        # 状态键与审计行同一事务提交：审计写不进 ⇒ 状态变更一并回滚
+        # （绝不留「改了但没审计」的窗口；失败必须可见，不得静默）
+        db.commit()
+    except Exception:
+        db.rollback()
+        logger.error(
+            "AUDIT_WRITE_FAILED tenant/switch from=%s to=%s user_id=%s source=%s "
+            "→ 审计写入失败，状态变更已回滚（无审计不得留变更）",
+            from_entity_id, data.entity_id, getattr(user, "id", None), data.source,
+            exc_info=True,
+        )
+        raise HTTPException(status_code=500, detail="审计写入失败，状态变更已回滚")
 
     return {"success": True, "current": state}