Harden UI layout for font scale and long strings

- Measure and cap the HUD target chip after each font-scale change; clip HUD top labels.
- Ellipsize long action-button labels so panels cannot grow past the viewport.
- Add accessibility/button layout assertions and refresh the gallery captures.
- Record the font/layout pass in TODO, docs, changelog and memory.

TODO.md

@@ -90,8 +90,10 @@ screen-design judge before any model/texture changes. No gameplay rules change.
       top-modal close path, menu/settings return handling and pointer recapture are
       recorded in `docs/ui-copy.md`; session smoke covers menu Settings, Help
       right-click and pause Settings.)
-- [ ] Test buttons at minimum/maximum HUD font scale and with 1.5–2× longer
-      strings; fix clipping, overflow and overlapping layouts.
+- [x] Test buttons at minimum/maximum HUD font scale and with 1.5–2× longer
+      strings; fix clipping, overflow and overlapping layouts. (Target chip now
+      measures/caps scaled text, HUD top labels clip, and action buttons ellipsize;
+      regression checks are in `test_accessibility.gd` and `test_ui_buttons.gd`.)
 - [ ] Test destructive/irreversible actions (campaign reset, tutorial replay,
       emergency send) require the intended confirmation/hold and cannot double-fire.
 - [ ] Verify radio normal-send vs emergency hold, inspection/wand allow/deny,