Phase 4 play-test fixes: deep caves, fuller cave spawns, strays, shared loot

From Adrian's play-test (2026-10-30):
- The Deep Dark no longer fills the deepslate layer: world/biomes.json
  splits it by temperature (Deep Dark under cold and temperate land,
  basalt deltas under the hottest, ordinary caves between); at y -52 it
  drops from 30 % to 14 % of the land, basalt 7 %.
- Cave zones fill up to their targets with lines whose primary type fits
  the cave; top stages spawn up to the band's top (Deep Dark Lv 60, Basalt
  70); no time-of-day conditions underground.
- Wild Pokemon more than 10 levels above the band of the zone they
  wander into despawn (zone/Wanderers.kt).
- Loot is shared: all players in one scoreboard team, Lootr team_loot.
- Basalt ore nodes reach the deep basalt.
Self-tests strays_despawn and loot_is_shared; the catching rules from the
previous commit are now tested too. Template rebuilt (world check passed),
island quick check passed (36 self-tests and the restart test).
Shoulder Pokemon noted for Phase 5.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

tools/zone_layout.py

@@ -313,6 +313,7 @@ def write_datapack(zone, plan, preview):
         "zones": [{k: z[k] for k in keep} for z in plan["zones"]],
         "caves": [{**{k: c[k] for k in keep}, "biome": c["biome"]} for c in plan["caves"]],
         "level_pressure": plan.get("level_pressure", {}),
+        "wanderers": plan.get("wanderers", {}),
         "samples": samples(zone, plan, preview),
         "biome_samples": biome_samples(zone, plan, preview),
         "grid_rle": runs,