fixed some files that were pointing towards base-game materials, mostly revolving around the antlion

headcrab had inconsistent filename

new models_ac directory for copied over pre-OB hl2 textures, currently featuring zombie and headcrab textures [and soon to be more]
this means certain textures are gonna be more era-accurate

this is different from the sniper ammo and censored zombie textures because those are transformative and obvious enough as custom content that they shouldn't pose any issues
models_ac is mostly for stuff that did change, but looks identical to post-OB's materials from a glance

⠀⠀⠀⠀⠀⠀⠰⡊⣿⣷⣂⠄⠀⠀⠀⠀⠀⠀⠀⠀
⠀⠀⣀⣴⢶⠀⠀⠈⣉⣽⣯⠃⠀⠀⠀⠀⠀⠀⠀⠀
⢀⢴⡿⡷⠁⣠⠊⠉⠂⠀⠀⠙⠒⠒⠒⠒⠢⢀⠀⠀
⡜⣿⣿⣵⣶⡃⠀⠀⢀⡤⠂⠈⠉⠀⣀⡀⠀⠀⢆⠀
⠙⠾⠿⠃⢹⠀⠀⠀⠀⠀⠀⠀⠀⠈⠋⠀⡀⠀⡞⠀
⠀⠀⠀⠀⠘⢆⠀⠀⠀⠣⣀⠀⠀⠀⢀⡴⠵⠊⠀⠀
⠀⠀⠀⠀⠀⠀⠑⣆⡤⠤⢬⠙⠉⡽⠋⢐⡲⢲⠀⠀
⠀⠀⠀⠀⠀⢰⡓⠃⠷⠤⠴⠗⠈⠉⠈⠁⣀⢰⠃⠀
⠀⠀⠀⠀⠀⠀⠥⣆⠖⠒⠢⡀⠀⠀⠈⢏⠈⠁⠀⠀
⠀⠀⠀⠀⠀⠀⠀⠀⠀⢗⣤⠁⠀⠀⠀⠀⠃⠀⠀⠀
⠀⠀⠀⠀⠀⠀⠀⢠⠊⢢⣇⠀⠀⠀⣀⢐⠗⡲⡰⢢
⠀⠀⠀⠀⠀⠀⠀⠘⡆⠀⠉⠠⢏⡁⢸⢇⠄⢆⠔⡸
⠀⠀⠀⠀⠀⠀⠀⠀⠈⠳⢤⣆⣂⡹⠸⣀⣃⡫⠞⠁

whoops! viewmodel

the only thing i changed from the original was giving the invisibility shader $nocull because i feel like it's better that way