Registers a paintApply SFX (with rate/volume jitter + a 60ms gap so rapid multi-face painting doesn't machine-gun), wires the sfx:paint-apply bus event, and emits it from the material-paint click chokepoint in the selection manager (fires on apply, not hover/preview). Adds the audio asset to the editor app's public resources. Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>