Bug: All lights do not ignore backfaces

[lunairekitty]

Describe the bug

In an issue existing in the Source engine since the beginning, lights are blocked by backfaces of a model even though this is illogical. This means you can't accurately put lights inside of a model and have it emit, rather requiring you to sacrifice shadows on that prop in order to use the light properly.

To Reproduce

1. Get a prop_static lamp model
2. Put a light inside it
3. Notice the light is blocked by the internal backfaces.

Issue Map

Not applicable/Any map

Expected Behavior

Lights should not be blocked by the culled backfaces inside of a model.

Operating System

Windows 11 25H2

[lenship2]

you can kind of get around this with clustered lights and the nearz parameter, but it obviously won't bake. i think having the nearz parameter affect baked lighting would be the most effective solution.

ignoring backfaces entirely might also break backwards compatibility with maps..