Bedrock provider was returning None for both streaming and non-streaming
inference, causing 'NoneType' object has no attribute 'choices' errors.
Primary fix: Reorder inheritance to put mixin classes before protocol class
in BedrockInferenceAdapter so actual implementations are called.
Additional AWS Bedrock API compatibility fixes:
- Fix non-streaming: use res["body"].read() instead of next(res["body"])
- Fix streaming: add proper event structure checks and safe access
- Disable repetition_penalty (not supported by Bedrock Llama models)
Fixes#3621
88e60c1bf6