Give the canvas tools a rail of their own, and the column one width

Crop, Local and Repair were chips at the head of the develop column, sharing a
row with the adjustment groups and told apart from them by the shape of their
highlight. Three things followed from that, and only the last is cosmetic: the
column closes, so the way out of a mode went away with the way in — hence the
duplicate "Done Cropping" over the canvas; the chips are generated from the
operation set, so the widest thing in the sidebar was a row nobody had chosen
the contents of; and a mode and a filter are different kinds of state wearing
one control.

They are a fixed 60px rail down the left now, generated from a single table in
toolrail.slint. A tool is one row of it plus a drawing plus a ViewMode variant;
nothing in app.slint is touched to add one. What is left of the strip is the
group filters, so it is GroupStrip.

The column stops measuring itself. Every panel published a content-width and
declared it as min-width, and the column took the largest — which spent the
photograph's pixels on whatever happened to be widest, and moved the image
sideways when switching tools swapped one set of panels for another. It is
panel-width now, one number in style.yaml.

That number is 360 and it is measured, not picked: the contents report a
minimum of 344 in every mode, and they do not compress below it because a Text
that does not elide reports the same minimum as preferred. 320 was tried and
sliced Paste down the middle. The Flickable's viewport is floored at the
layout's minimum rather than its preferred width for the same reason — content
that is never told how much room it has cannot adapt to having less.

Removing the eight content-width declarations repairs three comments an
earlier edit had spliced sentences into. The raw histogram's note on keeping
its hint short is rewritten rather than dropped: an over-long hint no longer
widens the column, it pushes the column's minimum past the width it has and
clips the panel, which makes that constraint sharper rather than obsolete.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

ui/dr-ui/ui/peaking.slint

@@ -79,18 +79,12 @@ export component FocusPanel inherits Rectangle {
 
     background: Theme.surface;
 
-    /// TRACES: FR-UI-2
-    /// How wide this panel has to be before it clips itself. The develop
-    /// column is the largest of these and nothing else; see `SpotPanel` and
-    /// `HistogramPanel` for the whole protocol.
-    ///
-    /// Both chip rows wrap at three, which is what keeps this number at the
-    /// narrowest column the application supports rather than at four chips
-    /// abreast — a single row of four would set the width of the entire
-    /// sidebar for every other panel in it.
-    out property <length> content-width: layout.preferred-width;
-    min-width: root.content-width;
-
+    // Both chip rows wrap at three rather than running four abreast. That was
+    // once about not setting the sidebar's width for every other panel in it;
+    // the column is a mandated `panel-width` now and no panel sets it, so what
+    // the wrap buys today is simply that these fit inside it rather than
+    // needing to be panned to.
+    //
     // Flat rather than nested, for the reason `SpotPanel` and `MaskPanel` both
     // give: a nested conditional layout under-reports its height here and the
     // rows below it get drawn on top of one another. Every row carries its own
@@ -140,9 +134,11 @@ export component FocusPanel inherits Rectangle {
             // frame cannot be measured for sharpness (see `FocusPeakPass`).
             //
             // Kept to one short sentence on purpose. A wrapping Text reports
-            // its *unwrapped* width as its preferred one, and this panel's
-            // `content-width` is what the develop column sizes itself from —
-            // a paragraph here would hold the whole sidebar open.
+            // its *unwrapped* width as its preferred one, so a paragraph here
+            // makes this panel's preferred width the length of the paragraph.
+            // That no longer drags the sidebar open with it — the column is a
+            // mandated width — but it does still decide how much of the row
+            // the panel wants, and a sentence is the honest amount to ask for.
             text: "Marks pause while a control is dragged.";
             wrap: word-wrap;
         }