Non-whitelisted MCP's keep connecting instead of showing error

### Short summary

Non-whitelisted MCP's keep connecting (showing spinner) instead of showing error

### Affected version or release

v1.0.23

### Installation context

_No response_

### What happened?

On an ghe.com with 'Restrict MCP access to registry servers' set to registry only when trying to use an non-whitelisted MCP server it keeps spinning/connecting instead of showing an error

### Steps to reproduce

1. Have 'Restrict MCP access to registry servers' set to registry only
2. Add non-whitelisted MCP server
3. MCP server keeps connecting/spinning

### Expected behavior

1. Have 'Restrict MCP access to registry servers' set to registry only
2. Add non-whitelisted MCP server
3. MCP server shows error / whitelisting error

### Additional context

_No response_

首先，在 ghe.com 上将“Restrict MCP access to registry servers”设置为“registry only”，重现该问题，然后添加一个不在白名单中的 MCP 服务器并观察连接状态。跟踪负责 MCP 连接失败的代码，并验证服务器停止转圈且显示白名单错误。

由索引模型根据 Issue 内容生成。