audit: route automation audit rows through hash-chain pair (gap 4, option A)

Bypass closed: automations._audit_row (direct audit_log INSERT,
best-effort swallow) is deleted. run_due_automation now writes via
cloud.auth.audit_on_conn, the same audit_log + audit_ledger pair
AuthStore.audit() writes, sharing created_at. The audit pair runs
before record_automation_run's commit, so task row, run row and
audit pair commit or roll back together; chain-head IntegrityError
retries the whole block up to 5 times, other errors roll back and
raise (fail-closed). The claim stays committed, so a failed run is
retried next interval, never recorded as a failed run.
AuthStore.audit() now delegates to audit_on_conn; its pair, retry
count and fail-closed semantics are unchanged.

cloud/auth.py

@@ -40,6 +40,55 @@ _ACTION_MIN_ROLE = {
     "manage_project": "owner",
 }
 
+# audit_log 建表 SQL（AuthStore.__init__ 与 audit_on_conn 共用同一
+# 份，绝不能各写一份后漂移）。PG 适配层把其中的
+# INTEGER PRIMARY KEY AUTOINCREMENT 翻译成 identity 列，见
+# cloud/db.py；SQLite 下原样执行。
+_AUDIT_LOG_TABLE_SQL = (
+    "CREATE TABLE IF NOT EXISTS audit_log("
+    "id INTEGER PRIMARY KEY AUTOINCREMENT, "
+    "user_id TEXT, "
+    "project_id TEXT, "
+    "action TEXT, "
+    "detail TEXT, "
+    "created_at REAL)"
+)
+
+
+def audit_on_conn(conn, user_id, project_id, action, detail="",
+                  created_at=None):
+    """在调用方给定的连接上写一对审计记录（单次尝试）。
+
+    与 AuthStore.audit() 是同一对写：audit_log 行 + audit_ledger
+    链条目同 created_at（调用方不给时取当前时间），先建两张表
+    （幂等），再写两行。本函数不 commit、不 rollback、不重试：
+    事务边界属于调用方——调用方须在自己的事务里 commit，失败
+    时 rollback 整段业务写、链头唯一冲突时 rollback 后重试整段
+    （只重试本对写会丢掉调用方同事务里已写但未提交的业务行；
+    见 cloud/ledger.py append_entry 的警告）。AuthStore.audit()
+    即本函数 + “自有连接上 commit、唯一冲突重试 5 次”的包装。
+
+    存在理由：automations.run_due_automation 拿到的是调用方连接
+    （任务 INSERT 与产出记录都在该连接的事务里），不能像服务端
+    handler 那样另开 AuthStore（自有连接、自有事务）去写审计——
+    那样审计与任务不在同一事务，审计失败时任务已落盘，所谓
+    “整对回滚”只保审计对、不保业务对。本函数让自动化执行器
+    的审计行与任务行、产出记录行同事务提交、同事务回滚。
+    """
+    if created_at is None:
+        created_at = time.time()
+    created_at = float(created_at)
+    conn.execute(_AUDIT_LOG_TABLE_SQL)
+    _ledger_ensure(conn)
+    conn.execute(
+        "INSERT INTO audit_log(user_id, project_id, action,"
+        " detail, created_at)"
+        " VALUES(?, ?, ?, ?, ?)",
+        (user_id, project_id, action, detail, created_at),
+    )
+    _ledger_append(conn, user_id, project_id, action,
+                   detail=detail, created_at=created_at)
+
 
 class AuthStore:
     """基于 SQLite 的用户 / 项目成员 / 审计存储。"""
@@ -61,15 +110,7 @@ class AuthStore:
             "role TEXT, "
             "PRIMARY KEY(project_id, user_id))"
         )
-        self.conn.execute(
-            "CREATE TABLE IF NOT EXISTS audit_log("
-            "id INTEGER PRIMARY KEY AUTOINCREMENT, "
-            "user_id TEXT, "
-            "project_id TEXT, "
-            "action TEXT, "
-            "detail TEXT, "
-            "created_at REAL)"
-        )
+        self.conn.execute(_AUDIT_LOG_TABLE_SQL)
         # 防篡改账本（哈希链）：audit_log 本身不动，链写进
         # audit_ledger；建表失败即建库失败，不静默丢链。
         _ledger_ensure(self.conn)
@@ -361,19 +402,17 @@ class AuthStore:
         “audit_log 有行、链上无行”的静默缺口）。并发抢链头
         导致唯一冲突时在事务边界重试整对写入，最多 5 次；
         其它错误直接回滚抛错，不重试。
+
+        实现即 audit_on_conn() + 本连接上的 commit/重试包装，
+        对写本身与 #241 完全一致（同一函数、同一 created_at
+        语义），不是第二套审计写路径。
         """
         now = time.time()
         last_exc = None
         for _attempt in range(5):
             try:
-                self.conn.execute(
-                    "INSERT INTO audit_log(user_id, project_id, action,"
-                    " detail, created_at)"
-                    " VALUES(?, ?, ?, ?, ?)",
-                    (user_id, project_id, action, detail, now),
-                )
-                _ledger_append(self.conn, user_id, project_id, action,
-                               detail=detail, created_at=now)
+                audit_on_conn(self.conn, user_id, project_id, action,
+                              detail=detail, created_at=now)
                 self.conn.commit()
                 return
             except Exception as exc: