Improve WebSocket probe to support non-redirect behaviours of corporate proxies

[nirben82]

Problem

The current WebSocket probe in #1391 detects session expiry by checking for opaqueredirect. This works for proxies that return a 302 Redirect on handshake.
However, other proxies might:

1. Return 200 OK but serve a login page HTML.
2. Return 401 Unauthorized or 403 Forbidden.
   In these cases, the current check fails to detect that re-auth is needed.

Proposed Solution

Observe additional proxy behaviours (such as returning HTML on 200, or 401/403 status codes) and update the probeConnection logic in channel.ts to handle them accordingly.