Phase 5: breeding with Cobbreeding, Ditto a rare Deep Dark find

Adrian (2026-10-31): add Cobbreeding without a gate; only Ditto should
be rare, in an endgame area or gated behind something else.

- Cobbreeding 2.4.1 (Modrinth only) and Cloth Config (client) in the
  pack; Cobblebase's hatchery takes Cobbreeding's eggs.
- Ditto moved from Button Isle to the Deep Dark with both of Cobblemon's
  entries (rare in slime chunks, ultra-rare elsewhere): zone_spawns.py
  pins take {"zone", "all_entries"}; Deep Dark target +1, Button Isle -1
  so no other line moved; Southwold and Frostpeak guardians pinned (they
  tie on base stats and flipped between runs).
- HMs' Trainer Ditto is made uncatchable; it still trades.
- check_deps.py skips other-side dependencies; Cobbreeding's harmless
  client-mixin log line allowlisted.
- Self-tests cobbreeding_eggs_fit_the_hatchery, trainer_ditto_cant_be_caught;
  docs, balance table, Phase 5 checklist.

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

mod/src/main/kotlin/dev/cobblesurvival/CobbleSurvival.kt

@@ -14,6 +14,7 @@ import dev.cobblesurvival.progress.Gates
 import dev.cobblesurvival.selftest.SelfTest
 import dev.cobblesurvival.world.OnlyPokemon
 import dev.cobblesurvival.world.SharedLoot
+import dev.cobblesurvival.world.SpecialPokemon
 import dev.cobblesurvival.zone.Guardians
 import dev.cobblesurvival.zone.InZoneCondition
 import dev.cobblesurvival.zone.LevelPressure
@@ -77,6 +78,7 @@ class CobbleSurvival {
         Catching.register()
         Wanderers.register()
         SharedLoot.register()
+        SpecialPokemon.register()
         ZoneHazards.register()
         LevelPressure.register()
         SelfTest.register()