test(ui): a component with no stylesheet reads the theme's :root variables

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

changes/defaults-views-templates.md

@@ -106,6 +106,8 @@ What a game's screens found missing, now in `ludic.ui`:
   `:capturing` while it listens;
 - a `title` shows for the keyboard's focus too, after the same half second; a focus ring drawn
   through a renderer with no `rect` no longer crashes;
+- a component with no stylesheet of its own reads a theme's `:root` variables from around it (it
+  did; now a test says so);
 - a transition lands exactly on its end value (it had stopped a rounding error short of it, at every
   frame rate).