幂等性：规范
使用调用者作用域键、规范请求指纹、持久结果状态、并发控制、过期以及成功和终止失败的安全重放来定义幂等变更语义。
Queues user mutations while offline with durable identity, ordering rules, retry and conflict policies, and user-visible queue state so reconnect does not replay or drop work unpredictably.