Extract Map Lights

Extract light sources from a BSP map. Returns lights from two sources: (1) entity lights — 'light' entities in the BSP entity lump with position, intensity, color, radius. (2) lightgrid-mined lights — inferred from the baked radiosity lightgrid by finding bright spots and clustering nearby samples. Useful for path tracing setup: pass extracted lights to the renderer's point light buffer. Parameters: include_lightgrid (default true), lightgrid_threshold (0-255, default 180), cluster_radius (Quake units, default 128).