The even halo read as decoration; dust reads as accumulation. The drift scatter now biases toward an airflow-shadow direction — fuller reach downwind, thinned upwind, slight center offset — still a pure deterministic function of the amount. Defense: a [TUNE] pass within the decided exposure form (mechanics/machine-work.md, amended with the uneven-settling note in this commit): density and spread still carry the amount, paused geometry still reads, no RNG or wall clock enters the renderer.