OIDC Auto-Discovery login not working in v2 web ui

[mlasevich]

Describe the bug

When trying to connect to http server that uses OIDC self-discovery with v2, the connection hangs and eventually fails.

The same URL works with V1.0.1 as well as with v2 in cli or tui mode - only broken in web mode

To Reproduce
Steps to reproduce the behavior:

1. Open in web mode
2. Create a new streamable http connection to an MCP with working OIDC discovery endpoints
3. Click on connect

Expected behavior
An OIDC/Oauth login initiated in a browser window.

Logs
There are no logs at all. Not even access logs :-/ --web --dev also does not work.

Additional context
Add any other context about the problem here.