Remove unused imports and variables

[Tet-9]

Removes unused imports and two unused locals flagged by ruff (F401, F841). No behaviour change; tests pass.

[ikeige-coder]

Thanks, but I'm closing this. It's lint-only cleanup across 9 files with no behavior change, and the repo doesn't enforce ruff, so nothing protects the result. Same reasoning as the #4 revert. If you add ruff to pyproject.toml and CI, I'll take the cleanup as a follow-up, since then it enforces something.