Squashed 'public/modelslib/' changes from 9445be8..7908551

7908551 Tortoise: Vants: avoid `random-seed`, use a different workaround
2edad5d CC Atmosphere: use fractional ticks and remove dark particles

git-subtree-dir: public/modelslib
git-subtree-split: 7908551233c3c89c7c6423e8e42c6d368e5e3e18
Merge commit 'f99bd72b65e65463f165b28986cb52e2a147f874'