0.0.20.16 — small meteor fallback + event meteor ore reward pass

Small legacy meteor worldgen:
- Restored only data/phayriosisreborn/forge/biome_modifier/small_meteor_biome_modifier.json.
- The old large meteor biome modifier remains removed. Do NOT restore it.
- SmallMeteorFeature now checks SmallMeteorWorldgenGate before its original Phase 1-2 condition.
- If the live meteor event is ON, legacy small meteor worldgen returns false and does not place.
- If the live meteor event is OFF, legacy small meteor worldgen behaves as it did originally.
- Gate priority: explicit file-config override -> pending Create World draft -> saved world setting -> fresh-world file default.
- This deliberately reuses the existing meteor.enabled setting; no duplicate config toggle was added.

Event meteor ore reward:
- Previous chamber target was 70-80 exposed ores (average ~75).
- New target is 127-173 exposed ores (average ~150), approximately double the previous ore count.
- The 49-entry ore pool now heavily favors rare rewards:
  * crimsonscale_ore: 12 entries
  * plutonium_ore: 9 entries
  * diamond_ore: 5 entries
  * emerald_ore: 4 entries
  * biometal_ore: 8 entries
  * iron_ore: 6 entries
  * copper_ore: 3 entries
  * gold_ore: 2 entries
- Rare group (crimsonscale + plutonium + diamond + emerald) is now 30/49 (~61%) of selections versus 11/49 (~22%) before.
- Ore placement geometry/chamber shape remains unchanged; only count and weighting changed.

Preserve:
- 0.0.20.15 common config system.
- Xaero map compatibility.
- Exact-target foliage/farmland behavior.
- Meteor flight, impact, shockwave collision fix, Nucleus guardian and one-shot event lifecycle.
