Remove unused imports (deque, sys, Opcode, struct, _REPLAY_ADJUSTABLE_OPCODES)
across 4 active Python files and refactor semicolons to separate statements
in radar_protocol.py. Add ruff lint job to CI workflow targeting only the
active files (excludes legacy GUI_V*.py and v7/).
Replace FT601Connection with FT2232HConnection in radar_dashboard.py and
smoke_test.py. Both files had broken imports after FT601Connection was
removed from radar_protocol.py. Also update requirements_dashboard.txt
(ftd3xx -> pyftdi) and GUI_versions.txt descriptions.