Type Alias StateChannel

The four material states every weathered asset understands, each 0…1:

• wetness: darker, more saturated albedo, glossy surface, drip streaks on walls, puddles on flat ground
• snow: snow settling on upward-facing surfaces, with noise-broken edges and sparkle
• burn: scorch → char → ash; foliage loses leaves (with heat, glowing ember cracks)
• damage: cracks, dents, darkening; missing pieces where cut-outs are allowed