- Add new racer spritesheets (8 angles × 64×64) for all 9 racers
- Introduce KART_ROT_FRAMES constant as single source of truth for rotation frame count
- Update SuperKartMode7.angleFrame(), SuperKartGame frame math, and procedural fallback
to derive from KART_ROT_FRAMES instead of magic numbers
- Update data/superkart-artwork.json with asset paths and 8-angle metadata
- Update sprites.md documentation to reflect 8-view-angle contract