Wrong Yellow RC3 giga grid V5.13

- Runtime gigas are restricted to dimension backrooms:backrooms AND biome backrooms:yellow.
- Monoroom/well runtime origins aligned to Y64/Y112/Y160 (worldgen visual origins).
- Wells use true /place jigsaw generation. Lateral base connectors were replaced by their final_state; vertical stage connector retained.
- Floor-specific stage pools keep caps at or below Y216. Estimated ceiling-piercing rates: low 30%, middle 32%, high 30% (about 31% overall).
- Splits are 50% east-west and 50% north-south. Reservations remain four 128x128 cells total.
