SmogThinner

Ties the district's air to the plot. It sits on the Smog entity and eases its VolumetricLighting and HeightFog densities between their thick values (volumeThick, fogThick, at Rules.state.smogLevel 1) and their clear values (at 0). It runs in edit and play, and re-pushes the global fog passes if another entity's teardown cleared them.