Fixed an issue where inventory items were lost; minor optimizations included. — Oxygen Train Steam update #1260172

0. Optimized character textures; fixed transparency issues with the beaver character's hair and the squirrel's clothing (shirt and pants).1. Replaced the small stone model to improve visuals and adjusted the contact angle between the stones and the terrain for a more realistic look.2. Fixed an issue where characters could not stand up after crouching.3. Further addressed the issue of inventory items disappearing upon opening the in-game backpack; if you encounter this problem, please contact the development team to receive a redemption code to reclaim your gear.