Phase 4: veins in every chunk, drops for the mobs the island lacks

Ore veins: make_world.py loads the island again row by row until
Regenerating Ore Veins has filled every chunk (/cobblesurvival veins
unfilled), cave tiers sit at their biome's depths, small zones get denser
veins, showcase veins are full size. The world report checks surface
tiers against the zone grid, cave tiers within two biome cells of their
cave, and fails on unfilled chunks; the template passes (37,689 chunks).

Drops: tools/drop_audit.py checks every creature drop a recipe or brewing
needs (docs/pokemon-drops.md). Blaze rods, ghast tears, breeze rods,
shulker shells and nether stars now drop from Pokemon through species
additions (self-test drop_additions_apply). The field guide counts vanilla
mobs as absent, applies species additions and reads the veins as sources.

Cobblebase tried (loads, self-tests pass) and left out until Adrian
decides its scope. Phase 4 checklist with the open questions.

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

tools/prism_instance.py

@@ -8,9 +8,10 @@ instance are left alone. Close the instance in Prism before syncing.
 
 When build/world-template exists (tools/make_world.py), it is copied into the
 instance as the save "Cobblemon Survival Island" unless that save already
-exists; --replace-world overwrites it.
+exists; --replace-world overwrites it, --save-name puts it into another save
+folder instead (e.g. next to a save someone has played).
 
-Usage: tools/prism_instance.py [--name NAME] [--prism-dir DIR] [--memory MB] [--replace-world]
+Usage: tools/prism_instance.py [--name NAME] [--prism-dir DIR] [--memory MB] [--replace-world] [--save-name NAME]
 """
 import argparse
 import json
@@ -64,6 +65,7 @@ def main():
     parser.add_argument("--prism-dir", type=Path, help="Prism data folder (auto-detected)")
     parser.add_argument("--memory", type=int, default=6144, help="max heap in MB")
     parser.add_argument("--replace-world", action="store_true", help="overwrite the island save in the instance")
+    parser.add_argument("--save-name", default="Cobblemon Survival Island", help="save folder for the world template")
     args = parser.parse_args()
 
     prism = args.prism_dir or next((d for d in PRISM_DIRS if (d / "instances").is_dir()), None)
@@ -81,7 +83,7 @@ def main():
     write_components(instance / "mmc-pack.json", pack["versions"])
     sync("client", game, stage)
 
-    template, save = ROOT / "build/world-template", game / "saves" / "Cobblemon Survival Island"
+    template, save = ROOT / "build/world-template", game / "saves" / args.save_name
     if (template / "level.dat").exists():
         if save.exists() and not args.replace_world:
             print(f"kept existing save {save.name} (use --replace-world to overwrite it)")