Do not entangle brush model loading with loading surface lights.
Do a separate pass over brush model surfaces for the sole purpose of
finding light sources. Enables consistent live-reloading light data
after patching entities/surface/rad files.
Instead of passing model color around as an implicit global state, pass it per-model.
This makes it (a) easier to track, (b) easy to fix blending issues. E.g. this fixes incorrect coloring of brush and studio models, which is also different.
still not fully there:
- glow is slightly off
- TransAlpha has wrong blending mode
apparently pipeline settings for brushes, models, and sprites are substantially different, need different pipelines