Fix CLI log level override and add regression test

[matdev83]

Summary

• ensure the CLI no longer overwrites configured log levels when no --log-level flag is provided
• add a regression test to confirm apply_cli_args preserves an existing logging level

Testing

• pytest tests/unit/test_cli_di.py::test_apply_cli_args_respects_existing_log_level -n 0
• pytest -n 0 (fails: missing optional test dependencies such as respx/pytest_httpx/hypothesis/freezegun/pytest_mock)

---

https://chatgpt.com/codex/tasks/task_e_68e6e2a7fa688333a4ac0711e7251bb9

[matdev83]

✅ APPROVED - This PR correctly fixes the CLI log level override bug.

Changes reviewed:

• Changed argument default from to in
• Updated help text to clarify the behavior
• Added comprehensive regression test

Verification completed:

• ✅ New test passes
• ✅ All existing CLI tests pass (163 passed, 2 skipped)
• ✅ No linting issues
• ✅ Logic correctly preserves existing log levels when no flag is provided
• ✅ Still allows explicit log level override via CLI flag

The fix is minimal, safe, and addresses the exact issue described. Ready to merge.

[matdev83]

✅ APPROVED - This PR correctly fixes the CLI log level override bug.

Changes reviewed:

• Changed --log-level argument default from INFO to None in src/core/cli.py
• Updated help text to clarify the behavior
• Added comprehensive regression test test_apply_cli_args_respects_existing_log_level()

Verification completed:

• New test passes
• All existing CLI tests pass (163 passed, 2 skipped)
• No linting issues
• Logic correctly preserves existing log levels when no --log-level flag is provided
• Still allows explicit log level override via CLI flag

The fix is minimal, safe, and addresses the exact issue described. Ready to merge.