mac skybox/terrain shader path renders skewed textures in sim

[utkarshgill]

bug

on mac, metadrive shader path renders sky textures skewed/folded (arrow-like artifact). this is visible in openpilot sim and reproducible with metadrive shader files in site-packages.
companion openpilot issue: commaai/openpilot#37526

observed files

metadrive/shaders/skybox_mac.frag.glsl
metadrive/shaders/skybox_mac.vert.glsl
metadrive/shaders/terrain.frag.glsl

screenshots

before (skewed sky/texture folding):

after local shader patch (artifact removed):

local patch that removes artifact

• update mac skybox shaders to modern path equivalent (#version 150, in/out, textureLod)
• replace deprecated texture2D(...) usage in terrain sampling path with texture(...) where needed for core profile behavior

notes

there is also a separate bgra channel-order bug in openpilot camera extraction. that is independent and on openpilot side. this issue is only about shader skew/folding on mac.