Tool tabs need a taxonomy, and the taxonomy was the problem: a table in
`ui/` mapping operation to tab breaks FR-DEV-3a, and a `group:` field risks
what `ui-refinement.md` condemned `starts-group` for — the core deciding
where the panel draws things.
`Attribute` threads the needle. It says what an operation *is* — tone,
colour, detail, optics, geometry, effect — which is the same category as
`ParamKind` and squarely on the core's side of ARCH §4.3a's line. What is
drawn, where it sits and whether it is visible stay the frontend's. There is
no attribute for "the third tab", the enum's order is declaration order
rather than screen order, and a frontend may render these as tabs, as
headings, or ignore them.
The payoff is that a tab strip can be *derived*: the groups are the
attributes present in the capability list, so the interface names no
operation and needs no table to keep in step. An operation joins the right
group by declaring what it is, which is the one thing its author is well
placed to say.
Plural, because the tone curve is genuinely both — an RGB curve is tonal and
the per-channel curves are chromatic, and filing it under one would hide it
from half the people looking for it.
Required and non-empty, enforced in `build.rs`, and the failure was checked
by removing the line rather than assumed. An operation with no attribute is
invisible to a panel that groups by them; a build that stops costs ten
seconds, a control nobody can find costs more. The vocabulary is closed for
the same reason: a typo would otherwise invent a category holding exactly one
operation, which looks like a deliberate one until somebody counts.
Six tests over the real chain, including the hand-written operations that
`build.rs` never sees and so cannot check.
The sidecar is authoritative — the catalog is a disposable index and the
RAW is never written — so a mask that does not round-trip is not a
persistence bug, it is lost work.
Layers get their own `[mask <version> <id>]` blocks rather than being
flattened into dotted keys. A layer is not a scalar: it carries a
selection, a geometry and a chain of its own, and encoding a region set as
`m1.region.0 = 12` would be neither readable nor mergeable. The version
uuid is repeated in the header instead of relying on the block following
its version, because "belongs to whichever version appeared above me" is a
relationship that hand-editing, merging and older builds each break
quietly.
Region ids sort and deduplicate on read rather than being trusted from the
file. The mask's identity is the *set*, so two devices writing the same
selection in different orders must produce the same mask rather than
argue about a difference that is not one.
Masks merge by layer id under FR-NC-9, which is the disjoint-survives rule
the parameters already follow one level up: a layer added on the phone and
one added on the desktop both survive. A layer *both* sides edited resolves
wholesale to the higher revision, because half of one selection plus half
of another's opacity is a layer neither person made. A remote deletion is
honoured, or a mask the user removed returns on every sync.
An unknown mask source is skipped rather than guessed at. Applying a newer
format's mask type as the nearest one this build knows would put a
confidently wrong adjustment on the photograph, which is worse than
applying none.
29 new tests. The interesting ones are about silence: a maskless version
clearing the previous image's layers, a bare selection persisting even
though it renders nothing, and a mask naming a version that is not in the
file being dropped instead of landing on whichever block was open.
dtourolle