Phase 3: Alpha guardians, one per zone, back 5 hours after a defeat

- Companion mod (zone/Guardians.kt): each zone's guardian stands at the
  zone's sample point, appears when a player is within 96 blocks, stays
  within 24 blocks, is uncatchable and half again as big. Beating it in a
  battle gives every player in the battle its drops; it returns after 5
  hours of game time (Adrian: fixed spots, 5 hours). State lives in the
  world save; /cobblesurvival guardians lists it.
- tools/zone_spawns.py writes data/cobblesurvival/guardians/<zone>.json:
  the strongest walking (or swimming) Pokemon of the zone at band top + 5,
  with the drops from world/zones.json. Boss drops follow Adrian's rule:
  Icy Rocks before Sunscorch, Heat Rocks before Frostpeak.
- Goat Fur and Hoglin Hide recipes make 8 per rock, so one guardian's 3
  rocks pay for one full insulating set.
- Self-test guardian_appears_and_returns; hazard tests cleaned up; the
  zone generator reads Cobblemon's own entries from the field guide's
  hidden_spawns.

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

docs/zone-species.md

@@ -57,3 +57,20 @@ Duskull (Dusclops, Dusknoir), Feebas (Milotic), Greavard (Houndstone), Mimikyu,
 ## Basalt Furnace (Lv 55–70, 9 lines)
 
 Charmander (Charizard), Durant, Gligar (Gliscor), Heatmor, Houndour (Houndoom), Magby (Magmortar), Sizzlipede (Centiskorch), Torkoal, Turtonator
+
+## Alpha guardians
+
+One per zone at its sample point, uncatchable, five levels above the band; it returns 5 hours after it is beaten. Its drops help with the next zone.
+
+| Zone | Guardian | Level | Drops |
+| --- | --- | --- | --- |
+| Button Isle | Pachirisu | 15 | 10× poke_ball, 4× potion |
+| Frostpeak Range | Tyranitar | 60 | 3× icy_rock, 2× exp_candy_l |
+| Sunscorch | Delphox | 50 | 3× heat_rock, 2× exp_candy_l |
+| Mangrove Mire | Arcanine | 43 | 3× icy_rock, 4× super_potion |
+| Verdant Jungle | Tangrowth | 35 | 8× pecha_berry, 2× exp_candy_m |
+| Highland Meadows | Cinderace | 40 | 3× icy_rock, 4× super_potion |
+| Westmarch | Carbink | 30 | 8× pecha_berry, 2× exp_candy_m |
+| Southwold | Sigilyph | 23 | 6× great_ball, 4× exp_candy_s |
+| Deep Sea | Kingdra | 55 | 1× mystic_water, 3× exp_candy_m |
+| Deep Dark | Dusknoir | 65 | 3× icy_rock, 2× exp_candy_l |