Surface SignalR Java WebSocket handshake HTTP errors

[HengYpinn]

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When negotiation is skipped, OkHttp reports a failed WebSocket upgrade through onFailure and includes the HTTP response. The Java client was discarding that response, so callers only saw a generic exception and couldn't handle status codes such as 401.

This surfaces non-101 handshake responses as the existing HttpRequestException, including the status code, while keeping the original OkHttp failure as the cause. Failures without an HTTP response keep their current behavior.

I added a regression test that serves a 401 response over a local socket and verifies the status code is available to callers.

Tested with ./gradlew spotlessCheck :test:test --no-daemon.

Fixes #47597

[dotnet-policy-service]

Thanks for your PR, @HengYpinn. Someone from the team will get assigned to your PR shortly and we'll get it reviewed.