fix: audit batch 1 (B-A migration audit_loop INTEGER, B-C gateway failure clears running slot)

- B-A: migrations.py tasks backfill loop now types audit_loop as
  INTEGER (other 6 columns stay TEXT), matching db.py backfill,
  server/worker ensure lists; TEXT readback '0' is truthy and
  would silently enable the audit loop for audit_loop=0 rows.
- B-C: gateway preparation failure early-return now calls
  _running_clear(task_id) next to _cleanup_task_seed, matching
  missing-key/repo/capability/tool gates; previously the capacity
  slot leaked until worker exit (default capacity 1 blocks reclaim).
- Tests: cloud/tests/test_audit_batch1.py (3 tests): migration
  ALTER types, INTEGER 0 readback not enabled via real worker
  row mapping, gateway failure clears slot and capacity reclaim.
  _claim doc 'three gates' list left unchanged (full early-return
  gate enumeration not verified this batch; residual wording).
- No other audit items touched (I-1..I-14, N-1..N-12).

cloud/migrations.py

@@ -221,15 +221,24 @@ def migrate_sqlite_to_postgres(sqlite_path, pg_conn=None, tables=None):
                         "PRAGMA table_info(tasks)").fetchall()}
                 except Exception:
                     _existing = set()
-                for _col in ("agent_name", "agent_version",
-                             "agent_instructions", "agent_tools",
-                             "agent_tool_approvals", "audit_loop",
-                             "audit_loop_packet"):
+                for _col, _coltype in (
+                        ("agent_name", "TEXT"),
+                        ("agent_version", "TEXT"),
+                        ("agent_instructions", "TEXT"),
+                        ("agent_tools", "TEXT"),
+                        ("agent_tool_approvals", "TEXT"),
+                        # 审计循环接线：开关列必须与 db.py 回填清单、
+                        # server/worker ensure 清单一致用 INTEGER；
+                        # 若建成 TEXT，PG 读回的 "0" 为真值，worker
+                        # 的 `or 0` 兜底拦不住，audit_loop=0 的
+                        # 历史任务会被悄悄当成启用（Audit batch 1）。
+                        ("audit_loop", "INTEGER"),
+                        ("audit_loop_packet", "TEXT")):
                     if _col not in _existing:
                         try:
                             pg_conn.execute(
-                                "ALTER TABLE tasks ADD COLUMN %s TEXT"
-                                % _col)
+                                "ALTER TABLE tasks ADD COLUMN %s %s"
+                                % (_col, _coltype))
                         except Exception:
                             pass
             if table == "task_followups" and "sender_task_id" in columns: