New speed_logic.py module converts raw CAN speed limit and GPS speed
into display-ready params. Called from controlsd (live) and
bench_onroad (bench) at ~2Hz. UI reads params to render:
- Current speed (top center, hidden when 0 or no GPS)
- MUTCD speed limit sign (lower-left, normal + nightrider styles)
- Unit-aware display (mph/kph based on CAN DISTANCE_UNIT)
Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>