fix(security): upgrade LocalCommandLineCodeExecutor warning to DeprecationWarning

[xr843]

Summary

Fixes #7462

The LocalCommandLineCodeExecutor currently emits a UserWarning at construction time to alert developers about unsandboxed code execution. However, UserWarning is easily suppressed in production configurations (e.g., python -W ignore, logging pipelines that filter warnings), which means the security message can be silently swallowed.

This PR makes the warning harder to accidentally suppress by:

• Upgrading from UserWarning to DeprecationWarning — visible by default in __main__ contexts and not filtered by standard production warning configurations
• Adding logger.warning() call — ensures the security message is visible in logging pipelines that don't capture Python warnings (dual-channel notification)
• Improving the warning message — clearer description of the risk with a link to the code executors documentation

Changes

• python/packages/autogen-ext/src/autogen_ext/code_executors/local/__init__.py:
  • Added module-level logger
  • Changed warning type from UserWarning to DeprecationWarning
  • Added logger.warning() for logging pipeline visibility
  • Improved warning message text with documentation link
• python/packages/autogen-ext/tests/code_executors/test_commandline_code_executor.py:
  • Added test for the new DeprecationWarning behavior

Backward Compatibility

This change is fully backward compatible:

• No API changes — constructor signature unchanged
• No behavioral changes — code execution works identically
• Warning is still emitted (just with a different type that is harder to suppress)
• Existing code that catches UserWarning broadly will still work since DeprecationWarning is a separate category

Test plan

• Existing tests should pass (warning type change does not affect restart test which uses a separate UserWarning)
• New test verifies DeprecationWarning is emitted on construction
• Manual verification: instantiate LocalCommandLineCodeExecutor and confirm warning is visible

🤖 Generated with Claude Code

[xr843]

@microsoft-github-policy-service agree

[xr843]

Hi team, just a gentle ping on this PR. CLA has been signed and all CI checks are passing. Happy to make any adjustments if needed. Thanks for your time!