Spawn C2ME Fix

Description

This mod patches AnimalVariantManager.chooseWeightedVariant() in the Spawn mod to use the entity’s own thread-safe RandomSource instead of Level.random.

This prevents a ConcurrentModificationException when C2ME calls finalizeSpawn from a worker thread during chunk generation, which would otherwise deadlock further chunk loading.

Additonally, it also fixes a threading conflict that could deadlock or crash the server during chunk autosave. Spawn’s block variant-assignment code (Moray Crevice, sea life decorations, sea urchins) occasionally performed unsafe world queries such as biome lookups, neighbor-block updates, from contexts where C2ME’s async chunk system could no longer guarantee they’d complete, causing server hangs. Block variant assignment is now deferred to run on a normal tick instead of during chunk autosave, and its biome lookup no longer forces a chunk load.

Known issues

The original approach was meant to make the animal variants deterministic, meaning you would always encounter the same variant in the same place in the world in the same seed. The fix breaks this behaviour and makes the variants completely random. Generating a world with the same seed will give you a different outcome each time.

There probably is a way to solve this more gracefully, but it would require much deeper integration which for me personally is out of scope.