WebSocket：验证与操作
定义经过身份验证的 WebSocket 连接的验证和操作，涵盖握手来源、消息授权、限制、存活性、背压、重连、部署排空和可观察性。
Collaborator presence is ephemeral and non-authoritative, expires without heartbeat, and reconnects with versioned session tokens so editing authority never derives from stale presence alone.