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>

tools/zone_spawns.py

@@ -23,7 +23,9 @@ datapacks/core/data/cobblesurvival/spawn_pool_world/<zone>.json:
      doesn't spawn there. If no stage fits, the closest one spawns across the whole band. Every
      stage that reaches the band spawns up to its top (Adrian, 2026-10-31; Cobblemon's own ranges
      stop where the next stage takes over, which left e.g. Dusclops at Lv 45–46 in the Deep Dark).
-  3. world/zones.json → "species" pins a line to a zone by hand: {"pikachu": "southwold"}.
+  3. world/zones.json → "species" pins a line to a zone by hand: {"pikachu": "southwold"}. The long form
+     {"ditto": {"zone": "deep_dark", "all_entries": true}} also keeps all of the line's entries when no stage
+     fits the band (otherwise the closest stage brings one entry).
   4. In cave zones every entry spawns in the cave's biome, and sky-light minimums, "can see sky", time
      of day, excluded biomes and the "natural" ground preset are dropped (there's no sky or day underground).
   5. Strong flyers (STRONG_FLYER_*) only spawn in zones whose band starts at HIGH_ZONE_LEVEL or more.
@@ -180,7 +182,9 @@ def main():
             continue
         lines[line_root(member, species)].append((entry, set(s["biomes"]), member, s["level"]))
 
-    pinned = {f"cobblemon:{k}" if ":" not in k else k: v for k, v in plan.get("species", {}).items()}
+    pins = {f"cobblemon:{k}" if ":" not in k else k: v for k, v in plan.get("species", {}).items()}
+    pinned = {root: pin["zone"] if isinstance(pin, dict) else pin for root, pin in pins.items()}
+    all_entries = {root for root, pin in pins.items() if isinstance(pin, dict) and pin.get("all_entries")}
     flying_lines = {root for root in lines if root in strong_flyers}
 
     def allowed(root, zid):
@@ -269,6 +273,8 @@ def main():
             # No stage reaches the band: the closest stage spawns across all of it.
             e, b, m, lv = min(usable, key=lambda u: min(abs(u[3][0] - hi), abs(u[3][1] - lo)))
             fitting = [(e, m, lo, hi)]
+            if root in all_entries:
+                fitting = [(ue, m, lo, hi) for ue, _, um, ulv in usable if um == m and ulv == lv]
         seen = set()
         for entry, member, a, b in fitting:
             spawn = copy.deepcopy(entry)