- Fixed AWS services failing silently on missing or invalid credentials.
  `AWSNovaSonicLLMService`, `AWSBedrockLLMService`, `AWSPollyTTSService`,
  and `AWSTranscribeSTTService` now push a fatal `ErrorFrame` with a
  "check AWS credentials and region" hint on auth-class failures, so the
  pipeline cancels promptly instead of continuing to run with no output.
- Fixed `AWSNovaSonicLLMService._disconnect` raising `InvalidStateError`
  from `awscrt/aio/http.py` when cleanup ran on a stream from a failed
  `invoke_model_with_bidirectional_stream` call. The error was masking
  the real connect-time auth failure in the logs.