Group the panel by what operations say they are about

A strip of groups over the adjust panel — Light, Colour, Detail — derived
from the attributes the operations declare. `adjust.slint` names none of
them: the strings arrive resolved and the panel only draws them, so a new
operation joins the right group by saying what it is and this file does not
change (FR-DEV-3a).

A group nothing carries is not offered, so a tab never opens onto nothing.
Geometry is left out because its one operation prefers an on-canvas widget
and is skipped by the row builder — a Geometry tab would be empty while
`GeometryPanel` holds the real controls. The strip appears only when there
is more than one group to choose between; a single tab is a control with one
option.

The selected group is underlined rather than filled. The accent means
*modified* everywhere else in this interface, and spending it on "which tab"
would blunt the one signal the panel has.

**The trap, and it nearly bit again.** `op_index` on a row counts over every
capability, not over the ones a filter kept — it is how a row routes back to
the core. Renumbering it while filtering would make a slider drive a
different operation, which looks like a rendering fault rather than a
routing one. `rows_filtered` keeps `enumerate` over the full list and only
`group_head` is a position within the emitted rows; a test moves a value
through a filtered row and checks it lands where it was asked to.

Six tests, including that a nonsense index falls back to showing everything
rather than to showing nothing.

ui/dr-ui/src/labels.rs

@@ -13,6 +13,15 @@
 pub fn resolve(key: &str) -> String {
     match key {
         // Operations
+        // The attribute names. Short on purpose: these are read as a strip
+        // of tabs, where a long word crowds out the next one.
+        "attr.tone" => "Light".into(),
+        "attr.colour" => "Colour".into(),
+        "attr.detail" => "Detail".into(),
+        "attr.optics" => "Optics".into(),
+        "attr.geometry" => "Geometry".into(),
+        "attr.effect" => "Effects".into(),
+
         "op.white_balance" => "White Balance".into(),
         "op.exposure" => "Exposure".into(),
         "op.highlights_shadows" => "Highlights & Shadows".into(),