Whether to use the learned denoise, and how much grain to keep, are what a
photographer sets, so they travel the one road every setting does: published
as a capability, captured by Preset, stored in the sidecar, replayed by the
undo stack (FR-DEV-3c). Published only on a photograph that can take it, for
the lens switch's reason; the availability is derived from the file and is
not in the state. Off by default, grain 0; a reset returns both.