Theme · Editing: segments that give way, every color named

SegmentedControl's segments now give way when narrow, their labels
ending in an ellipsis, down to twice a control's height each; past
that the strip scrolls as before. The pill's border and padding moved
onto the scrolling strip, and the row inside it takes that floor as its
least width, so the strip scrolls exactly to its last segment. The
palette macro now writes each color's name from its field: Palette and
Syntax gain NAMES and token_mut for every color, the quiet fills too.
Tests press a density segment and each slider, and fit the density
strip in 280px with the text a step and a half larger.

TASKS.md

@@ -419,3 +419,4 @@ Per-component lines live in `tasks/`. Tags there:
 | T38a | 1 | FAIL | the resize grip and edge handles hung half outside the box; the edges' sides, a free turn and a band with Shift untested |
 | T38a | 2 | PASS | |
 | T38b | 1 | PASS | |
+| T39a | 1 | FAIL | a larger text size cut the density strip at 280px; ten palette colors had no name; the density and sliders untested |