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>

docs/design.md

@@ -128,6 +128,22 @@ Order of play the bands suggest: Button Isle → Southwold → Westmarch or Jung
 - Cold Sweat's own animals (chameleons) can't join, like vanilla mobs: the only-Pokémon rule now lets in Cobblemon's entities only.
 - Tested on the island itself (`cold_needs_fur`, `heat_needs_hide`, `lowlands_are_mild` in `tools/quick_check.py`): players stand at real spots in each zone, their body drift is turned into minutes until it hurts, and a frozen player without the grace period takes damage.
 
+## Phase 4: resources (in progress, placeholders until Adrian approves)
+
+**Ore veins.** Ore only comes from [Regenerating Ore Veins](https://www.curseforge.com/minecraft/mc-mods/regenerating-ore-veins) (plus chest loot): a mined vein block turns into a regenerator and grows back after its time, which counts in real time, unlike the guardians' game time. Each ore tier has veins in exactly one zone, higher tiers in higher zones (table in `docs/balance.md`). `tools/zone_ores.py` writes the mod's config (`pack/config/regenerating_ore_veins/`) from `world/zones.json` → `ores`:
+
+- A surface zone is a set of boxes cut from the zone grid; the mod checks every block of a vein against them, so no vein block lies outside its zone. Cave biomes are zones of their own, so surface tiers stay out of them; the mod checks the biome only at a vein's centre, so a vein's edge can reach up to two blocks over a cave border. Cave tiers are limited to their cave biome and the depths where it lies (the Deep Dark mostly below y −24, the others between 0 and 40).
+- Tiers with an ordinary and a deepslate ore get two veins: the ordinary ore from y 0 up, the deepslate one below.
+- **Cobblemon's evolution stones are tiers too** (new in Phase 4, flagged): their natural ores have been off since Phase 1, so stones had no source. Each stone lives in one zone that fits it (Leaf Stone in the jungle, Water Stone in the Mire, Ice and Dawn Stone on Frostpeak, ...).
+- Players can't break regenerators (`allow_breaking` false), so nobody removes a vein for good, and explosions don't hurt veins. The Vein Locator is crafted from a compass and a copper ingot instead of netherite.
+- The mod fills a new chunk with veins only while the chunk is loaded, 8 chunks a tick, and forgets the rest when the server stops. Pregeneration is faster than that, so `tools/make_world.py` loads the island again row by row until every chunk is filled (`/cobblesurvival veins unfilled` counts what's left), and the world report fails on any unfilled chunk. On a live server new chunks fill as players load them.
+- One showcase vein per surface zone (its first tier) sticks out of the ground near the zone's sample point, so players see what a vein looks like before they dig.
+- Checked: the world report (ore only in tracked veins inside their tier's zone, every tier present, every chunk filled) and the self-tests `vein_regrows_after_unload` and `vein_regrows_after_restart` (a second server start in `tools/selftest.py` and `tools/quick_check.py`).
+
+**Unique drops.** Only Pokémon live on the island, so a mob's drop needs another source. `tools/drop_audit.py` checks every item a Pokémon or a vanilla mob drops that a recipe or brewing consumes, and writes `docs/pokemon-drops.md` (item, wild Pokémon with zone and chance, other sources, consumers). Gaps it found, filled through Cobblemon species additions (`datapacks/core/data/cobblesurvival/species_additions/`, placeholders): Blaze Rod (Carkol in Westmarch, Torkoal in the Basalt Furnace; needed for brewing stands, blaze powder and Eyes of Ender), Ghast Tear (Drifloon, Dusclops), Breeze Rod (Whimsicott), Shulker Shell (Shuckle, Cloyster), Nether Star (Charizard). The tide armour trim and the wither skeleton skull stay without a source (cosmetic here). A zone spawn with its own drops overrides the species' drops, so the audit also fails if an addition targets such a spawn (Magmortar's and Centiskorch's did). Self-test: `drop_additions_apply`.
+
+The field guide learned two things on the way: vanilla mobs count as absent (the companion mod lets only Cobblemon's entities join a world), and species additions replace the drops they set. The veins come in as sources from `world/vein-sources.json`.
+
 ## Open decisions for Adrian (proceeding with the default, flagged)
 
 | Decision | Default used for now |