PLN: 'dont HL when d1-d12 controls are at zero volume (so D1 at 0 kills
d1 HLs, A1 at 0 kills d9, etc)'. A trigger the mix cannot hear is not a
picture the lens should paint. Only a KNOWN zero gates — a fader never
touched is unknown, not silent. Existing glow decays naturally instead of
vanishing mid-note.