username with @ character error

When the username (-U) contains an @, it will assume a username on the left side and a server address on the right side of the @.

appending an extra @ followed by the same value of server (-S) fixes the issue, and it now uses the correct username and server address to sign in.

it seems to me this behavior should be fixed, since server address is a separate input argument. Or documenting this on the username argument description.

首先跟踪 CLI 在登录前如何解析用户名 (-U) 和服务器 (-S) 参数。复现用户名中包含 @ 的情况，然后验证用户名得以保留，并且服务器仍从 -S 获取，无需额外的 @。

由索引模型根据 Issue 内容生成。