chore(migration): 登记 Worker 负载迁移安全审查

基于宁波生产 PostgreSQL 18 的只读预检，gateway_worker_instances 当前为 96 行、180224 字节，常量默认值新增列不会触发表重写，回填和约束验证范围可控。\n\ngateway_concurrency_leases 仅增加可空列；记录迁移校验器允许的 non-null column addition，并保留迁移文件不可变。\n\n验证：node scripts/ci-validate-migrations.mjs ac8d6dcf452ac555eb344f76caf6965c2ea42a97；./tests/ci/migrations-test.sh

scripts/migration-safety-reviewed.json

@@ -30,6 +30,13 @@
         "destructive DROP operation"
       ],
       "reason": "The migration replaces only the existing Worker status CHECK constraint so a rolling deployment can mark lost instances stale. It does not drop data, columns, tables, or indexes; the old and new binaries both continue to read active and draining rows safely."
+    },
+    "apps/api/migrations/0101_worker_adaptive_load.sql": {
+      "sha256": "4a23a194b9244f0afe245ceb8ff47ee03ca7d3e732e5593f731380bdf3dd77ae",
+      "allowedViolations": [
+        "non-null column addition"
+      ],
+      "reason": "The adaptive Worker columns use constant defaults on gateway_worker_instances, so PostgreSQL 18 can add them without rewriting the table. Production preflight on 2026-08-03 found 96 rows and a 180224-byte relation; the explicit backfill and constraint validation are therefore bounded. The only change to the 31899648-byte gateway_concurrency_leases relation is a nullable numeric column and a NOT VALID check followed by validation."
     }
   }
 }