fix: store AgentCore browser client for proper session cleanup

[omerio]

Description

The session_client was not being stored in _client_dict after creation in create_browser_session(), causing close_platform() to iterate over an empty dict and never call client.stop() to terminate AgentCore browser sessions.

This resulted in:

Browser sessions remaining in "READY" status in AWS Console after calling close()
The close() action returning success but not actually terminating the remote session
Applications hanging indefinitely as reported in #205
This fix adds a single line to store the session_client in _client_dict using the session_id as the key, allowing close_platform() to properly terminate all sessions when the browser is closed.

Related Issues

Fixes #205

Documentation PR

N/A - No documentation changes required for this bug fix.

Type of Change

Bug fix

Testing

Tested manually by:

Creating an AgentCore browser session
Performing browser actions (navigate, get_text, screenshot)
Calling close() action
Verifying via AWS CLI that sessions are now properly terminated (status: TERMINATED) instead of remaining in READY state
aws bedrock-agentcore list-browser-sessions --browser-identifier aws.browser.v1 --region us-west-2
Before fix: Sessions remained in READY status after close After fix: Sessions properly show TERMINATED status

• I ran hatch run prepare

Checklist

• [x ] I have read the CONTRIBUTING document
• [x ] I have added any necessary tests that prove my fix is effective or my feature works
• [N/A] I have updated the documentation accordingly
• [N/A] I have added an appropriate example to the documentation to outline the feature
• [ x] My changes generate no new warnings
• [ x] Any dependent changes have been merged and published

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