test: add unit tests for TypeScript ChainAgent and BedrockFlowsAgent

[nuthalapativarun]

Problem

ChainAgent and BedrockFlowsAgent have no unit test coverage in the TypeScript package. The only agent tests that exist are LambdaAgent.test.ts, OpenAi.test.ts, and the general Agents.test.ts.

Proposed Solution

Add typescript/tests/agents/ChainAgent.test.ts and typescript/tests/agents/BedrockFlowsAgent.test.ts following the same patterns used in LambdaAgent.test.ts:

• Mock the AWS SDK / external clients
• Test processRequest happy path
• Test error / edge cases

This mirrors the work done in Python (#457-style) for the TypeScript side.

[cornelcroi]

PR #540 implements exactly this. Closing the issue — it will be resolved when #540 is merged.