SKYBOX_FORCE_SUN_SHAFTS (0x8) and SKYBOX_NO_SUN_FOG (0x10) constants, CameraSkybox::flag_weight (heaviest main layer carrying a flag). update_fog_model scales sun_fog_strength by 1 - weight of a 0x10 sky. LIGHTING.md documents both flags (0x8 consumer lands in the next commit). Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>