Support for Bedrock models

[raccad]

Would love support for bedrock models.

[tnm]

Good idea. Can you tell me a little more on this, e.g., specific models or just anything on bedrock?

[alesauce]

@tnm
I'd like to add my support for this feature request! I'm in a similar situation where I need to use AWS
Bedrock instead of external API providers due to organizational compliance policies. Plus, this would enable access to all Bedrock-supported models. I'm happy to implement this feature if you're supportive of the direction. I can open a PR with the changes and work with you on any adjustments needed.

Proposed Implementation

I've reviewed the codebase and it looks like adding Bedrock support would be fairly straightforward by
following the existing provider pattern:

1. New configuration class in src/kit/summaries.py for Bedrock-specific settings
2. Client factory addition in src/kit/llm_client_factory.py using boto3 and Bedrock's Converse API
3. PR review integration in src/kit/pr_review/config.py to support bedrock as a provider option
4. Dependencies update in pyproject.toml to add boto3 as an optional dependency
5. Authentication via standard AWS credential chain

Estimated scope: ~150-200 lines across 4 files

Questions for Maintainers

If you would like me to take a stab at the implementation:

1. Architecture preferences? Does my proposed approach align with your vision, or would you prefer a different structure?
2. Testing requirements? What level of coverage would you want for AWS-specific code?
3. Documentation needs? Dedicated Bedrock guide or additions to existing docs?