Phase 6 0.0.17 catastrophic-impact expansion

- Real explosion power 30; this is the only authoritative blast.
- 120x flying render, 23x12 physical meteor, 60-block infection footprint.
- 72-block decaying radial shockwave + expanding visual rings.
- Sparse magma patches around impact.
- Small upper chamber/tunnel, 10-13 weighted single-block ores only.
- Exterior spawn wave: 3 converted_human, 2 patroller, 2 infester, 1 gory_mass.
- One chamber Nucleus; only that spawned instance gets max/current health 500.
- Impact chunk radius 4, tickets held 120 ticks then released.
- Preserve one genuine Level explosion for Explosion Overhaul/Sound Physics integration.
