Wrap the falloff and edge chips so a category mask cannot widen the column

Five chips in one row declare 440px, and the develop column takes the
widest panel's request — so selecting a category mask levered the sidebar
past the window's edge, clipping the histogram, the group strip and the
subject list. The same trap ChipGrid's comment records for film formats.

ui/dr-ui/ui/masks.slint

@@ -713,10 +713,17 @@ component MaskEntry inherits Rectangle {
                 reset => { root.feather-changed(0.004); }
             }
 
+            // Wrapped, both of them: five chips in one row is 440px of
+            // declared width, and in this column the widest panel's request
+            // is what every panel gets — selecting a category mask levered
+            // the whole sidebar open past the window's edge and clipped the
+            // histogram, the groups strip and the subject list along with
+            // it. See `ChipGrid`.
             if root.data.shapeable: Segmented {
                 label: "Falloff";
                 options: ["Hard", "Linear", "Smooth", "Gaussian", "Expo"];
                 selected: root.data.falloff;
+                columns: 3;
                 picked(i) => { root.falloff-picked(i); }
             }
 
@@ -726,6 +733,7 @@ component MaskEntry inherits Rectangle {
                       + "pinholes; open removes specks.";
                 options: ["None", "Grow", "Shrink", "Close", "Open"];
                 selected: root.data.morphology;
+                columns: 3;
                 picked(i) => { root.morphology-picked(i); }
             }