Phase 3: soft level pressure, less experience far above a zone's band

- Companion mod (zone/LevelPressure.kt): a Pokemon more than 5 levels
  above the band of the zone its trainer is in gets 10% less experience
  per extra level, down to 10%. Exp. Candy and commands are exempt; no
  hard level caps (roadmap).
- Rules in world/zones.json -> level_pressure, shipped in the zone layout.
- Self-test level_pressure_cuts_xp.

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

docs/design.md

@@ -111,6 +111,8 @@ Order of play the bands suggest: Button Isle → Southwold → Westmarch or Jung
 
 **The Mire's poison** (Phase 3, step 5): while a player is in the Mangrove Mire without Mire Waders on, the companion mod gives them Poison every 5 seconds (`zone/ZoneHazards.kt`, data in `datapacks/core/data/cobblesurvival/zone_hazards/mire.json`, protection tag `#cobblesurvival:mire_protection`); the first time they walk in unprotected they get a warning. Vanilla Poison never kills, but it pins a player at half a heart, so a fall or a Pokémon's hit becomes deadly; milk, potions and golden apples still help. Mire Waders (leather boots, a KubeJS item) drop from the guardians of Westmarch and the Verdant Jungle, the zones before the Mire. Tested: `mire_poisons_without_waders`.
 
+**Soft level pressure** (Phase 3, step 6; no hard level caps): a Pokémon more than 5 levels above the band of the zone its trainer is in gets 10 % less experience per extra level, down to 10 % (`zone/LevelPressure.kt`, values in `world/zones.json` → `level_pressure`). It counts battle experience and anything else except Exp. Candy and commands. The roadmap also offered a disobedience chance; experience alone is gentler and Cobblemon has nothing to build disobedience on. Tested: `level_pressure_cuts_xp`.
+
 **Alpha guardians** (Phase 3, step 4; Adrian, 2026-10-29: fixed spots, back 5 hours after being beaten):
 - One per zone except the Shallows, Lush Caves and Dripstone; the Basalt Furnace gets its boss in Phase 7. Each stands at its zone's sample point (deep inside the zone; a cave floor for the Deep Dark) and only appears while a player is within 96 blocks; it wanders no further than 24 blocks.
 - The guardian is the strongest Pokémon that spawns walking (or, at sea, swimming) in its zone, five levels above the band, half again as big, and uncatchable: Pachirisu (Button Isle), Sigilyph (Southwold), Carbink (Westmarch), Tangrowth (Jungle), Arcanine (Mire), Cinderace (Highlands), Delphox (Sunscorch), Tyranitar (Frostpeak), Kingdra (Deep Sea), Dusknoir (Deep Dark). `world/zones.json` → `guardian.species` overrides the pick.