[CI] Ruff lint check failing — needs investigation and fix

[RobLe3]

Summary

The `Lint (Ruff)` CI job has been failing since 2026-05-19 (3+ days). All other jobs (tests, typecheck, security, conformance) are passing.

Impact

Every push to `main` shows a red CI badge. Operator confidence eroded; no new commits can be verified clean until this is resolved.

Steps to reproduce

git clone https://github.com/RobLe3/iicp-client-python
pip install ruff
ruff check src tests

Expected fix

Run `ruff check src tests --fix` and/or `ruff format src tests` locally, then commit the result. Ruff config in `pyproject.toml`:

[tool.ruff.lint]
select = ["E", "F", "I", "UP", "B"]

Context

Detected by IICP monorepo REPO-HEALTH audit (2026-05-22). Cross-tracking issue filed in main repo.