Event objects like Fire Festival Fury Trap and Mercutio Post use
SpellObject_InvisibleTrap.m2 models which were rendering as white
tiles using WHITE1.BLP texture. These are meant to be invisible
spell trigger objects that should not obstruct player movement.
Changes:
- Added isInvisibleTrap flag to M2ModelGPU struct
- Detect models with "invisibletrap" in name during loading
- Skip rendering invisible trap instances in render loop
- Disable all collision checks (floor/wall/occlusion) for invisible traps
- Objects remain functional for spell casting but are now invisible
