fix: apply consistent origin checks to WebSocket redirects (#3693)

## Summary

Apply consistent origin checks to WebSocket redirects across async
Realtime and Responses, including reconnections. Reuse the existing
Azure guard while preserving same-origin redirects, Azure behavior, and
synchronous behavior.

## Validation

- 148 focused tests passed, including socket-free redirect and reconnect
regressions.
- Compatibility checks passed with websockets 13.0, 13.1, 14.0, 14.2,
and locked 15.0.1.
- Repository lint, Pyright, mypy, and import checks passed.
- No dependency changes.