Submission containing a code fix for the lighting sampling issues that almost all cosmetics in the game suffer.
The example images above demonstrate the bug, with the lighting sample positions visualized.

Technical Description:
All models sample their ambient lighting from a vector (named illumination position, or illumpos) which each model has.
Most cosmetics and weapons included in the game do not have a correctly positioned illumpos.
This results in discrepancies between the ambient lighting of the player model vs the cosmetics, which looks visually ugly.
In certain situations, this can put a player at a disadvantage as their cosmetics brighten up in a darkly lit room, as the illumpos extends into a different area.
The fix is simple, it overwrites the cosmetic, weapon and viewmodel lighting origins to sample from its owner's position instead, so the discrepancies no longer appear.

Part of the TF2 Community Fix-Up Pack: https://steamcommunity.com/workshop/filedetails/?id=2156577890