feat(code_interpreter): support custom boto3 session for cross-account access

[funkiben]

Description

Closes #495
Adds a boto_session parameter to AgentCoreCodeInterpreter that gets passed through to the underlying BedrockAgentCoreCodeInterpreterClient, enabling cross-account access.

Related Issues

#495

Type of Change

Other (please describe): New feature — adds an optional parameter to an existing tool

Testing

Ran unit tests for the code interpreter module. All 54 tests pass including 3 new tests covering:

• Initialization with a custom boto3 session

• init_session passes the boto3 session to the underlying client

• _ensure_session passes the boto3 session when reconnecting via module cache

• I ran hatch run prepare

Checklist

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

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[gautamsirdeshmukh]

/strands review

[github-actions]

Assessment: Approve

Clean, well-scoped change that adds cross-account access support via an optional boto_session parameter. The implementation is consistent with the existing pattern in agent_core_memory.py, both client creation points are correctly updated, and the tests cover initialization, session creation, and reconnection paths.

No issues identified.