feat(api): unify Bedrock provider using Runtime API

Problem:
The current Bedrock implementation uses the Bedrock SDK, which requires separate handling for different model types and doesn't provide a unified streaming interface.

Solution:
Integrate the Bedrock Runtime API to provide a single, unified interface for all Bedrock models (Claude and Nova) using the ConverseStream API. This eliminates the need for separate handlers while maintaining all existing functionality.

Key Changes:
- Refactored AwsBedrockHandler to use @aws-sdk/client-bedrock-runtime
- Enhanced bedrock-converse-format.ts to handle all content types and properly transform between Anthropic and Bedrock formats
- Maintained cross-region inference support with proper region prefixing
- Added support for prompt caching configuration
- Improved AWS credentials handling to better support default providers
- Added proper error handling and token tracking for all response types

Dependencies:
- Added @aws-sdk/client-bedrock-runtime for unified API access
- Removed @anthropic-ai/bedrock-sdk dependency

Testing:
- Verified message format conversion for all content types
- Tested cross-region inference functionality
- Validated streaming responses for both Claude and Nova models

This change simplifies the codebase by providing a single, consistent interface for all Bedrock models while maintaining full compatibility with existing features.

package-lock.json

@@ -11,6 +11,7 @@
         "@anthropic-ai/bedrock-sdk": "^0.10.2",
         "@anthropic-ai/sdk": "^0.26.0",
         "@anthropic-ai/vertex-sdk": "^0.4.1",
+        "@aws-sdk/client-bedrock-runtime": "^3.706.0",
         "@google/generative-ai": "^0.18.0",
         "@types/clone-deep": "^4.0.4",
         "@types/pdf-parse": "^1.1.4",