feat: set client info in user agent in header

[wzxxing]

Summary

Changes

Please provide a summary of what's being changed

Requested by partner teams.

User experience

Please share what the user experience looks like before and after this change

No change to the user experience

Test

Connect to my bedrock runtime, client info user agent is in the headers.

2025-11-27 19:22:15.671 [warning] [test] Log from MCP Server: 2025-11-27 19:22:15 | DEBUG | 
mcp_proxy_for_aws.sigv4_helper | Request headers after signing: Headers({'connection': 'keep-alive', 'host': 'bedrock-
agentcore.us-west-2.amazonaws.com', 'accept-encoding': 'gzip, deflate', 'user-agent': 'kiro/0.0.0 mcp-proxy-for-aws/1.1.2', 

Checklist

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• I have reviewed the contributing guidelines
• I have performed a self-review of this change
• Changes have been tested
• Changes are documented

Is this a breaking change? (Y/N)

• Yes
• No

Please add details about how this change was tested.

• Did integration tests succeed?
• If the feature is a new use case, is it necessary to add a new integration test case?

Acknowledgment

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