- Add Coinage (1 shield → 1 gold) and Public Works (2 shields → 1 food)
special build options for cities, with remainder carry logic in shieldBox
- Update AI to fall back to producing gold or food instead of stockpiling
redundant defenders when nothing else is available
- Fix mid-build detection to check build.type before comparing shield progress
- Add City Screen UI for special builds: display gain per turn, color-coded
rows, and tooltips
- Only apply class-switch penalty when switching between unit/building
production types
- Add verification tests for coinage payout, public works remainder carry,
and AI special build fallback
feat(superkart): fix player kart scale + add missing backdrop images
- Compute PLAYER_KART_SCALE from MODE7 parameters instead of hardcoding,
keeping player and AI karts consistent at the camera's follow distance
- Wire up previously null backdrops: volcano, scrapyard, swamp, speedway,
nightcity