Show the colour mixer as three runs of twelve, each row a colour

The mixer was thirty-six sliders reading "Hue / Sat / Lum" twelve times
over with nothing saying which band any row belonged to. The identity was
there all along — the descriptor declares param.mixer.orange.sat and BANDS
carries orange at 30° — and was discarded on the way out: labels.rs had no
mixer entries, so every key fell through to a derived label that yields the
bare channel name.

A parameter can now say which aspect it adjusts and which subject it
adjusts it on, with the subject's hue where the subject is a colour
(descriptor::Facet). That is data about what the operation does, not a
layout: the mixer genuinely weights pixels around 30°. What to draw from
30°, and in what order to stack the runs, stay in dr-ui (ARCH §4.3a) —
develop.rs brings rows sharing an aspect together and marks the first of
each, and adjust.slint names the run once and draws a swatch, a track and a
readout on one line.

Grouped by channel rather than by band because an edit is almost never
"everything about orange"; it is the saturation of the greens, made by
comparing one channel across neighbouring bands. Twelve band sections put
those twelve rows in twelve different places.

The swatch is the label, which is what makes twelve rows fit where four
did. The band name is not lost: it is the row's accessible label, so the
control is not colour-only, and labels.rs is where the mapping is written
down — including chartreuse as "Yellow-Green" and spring as "Blue-Green",
since nobody hunting foliage scans a list for "Spring".

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

ui/dr-ui/src/labels.rs

@@ -20,6 +20,7 @@ pub fn resolve(key: &str) -> String {
         "op.brilliance" => "Brilliance".into(),
         "op.vibrance" => "Vibrance".into(),
         "op.saturation" => "Saturation".into(),
+        "op.colour_mixer" => "Colour Mixer".into(),
         "op.framing" => "Crop & Rotate".into(),
 
         // Parameters
@@ -34,6 +35,37 @@ pub fn resolve(key: &str) -> String {
         "param.vibrance" => "Vibrance".into(),
         "param.saturation" => "Saturation".into(),
 
+        // What a faceted parameter adjusts — the mixer's three channels.
+        //
+        // Spelled out rather than left to `derive`, which would give "Sat" and
+        // "Lum" from the keys. These name a run of twelve rows apiece, and an
+        // abbreviation at the head of a section is a word the reader has to
+        // expand every time they scan past it.
+        "param.channel.hue" => "Hue".into(),
+        "param.channel.sat" => "Saturation".into(),
+        "param.channel.lum" => "Luminance".into(),
+
+        // The hue bands, which a faceted row is *subject* to.
+        //
+        // Catalogued even where `derive` would produce the same word, because
+        // three of them are not the word the key spells: "spring" is spring
+        // green, and reading "Spring" beside "Green" in a list of colours says
+        // nothing. These are also the only place a swatch's meaning is written
+        // down in words, which is what a photographer who cannot separate the
+        // squares by eye has to go on.
+        "band.red" => "Red".into(),
+        "band.orange" => "Orange".into(),
+        "band.yellow" => "Yellow".into(),
+        "band.chartreuse" => "Yellow-Green".into(),
+        "band.green" => "Green".into(),
+        "band.spring" => "Blue-Green".into(),
+        "band.cyan" => "Cyan".into(),
+        "band.azure" => "Azure".into(),
+        "band.blue" => "Blue".into(),
+        "band.violet" => "Violet".into(),
+        "band.magenta" => "Magenta".into(),
+        "band.rose" => "Rose".into(),
+
         // Framing. "Straighten" rather than "Angle" because that is the task
         // the control performs; the number it reports is still degrees.
         "param.angle" => "Straighten".into(),