fix(ui): calmer PreferenceSwitcher panels and static StatsBar items

PreferenceSwitcher: theme choice is a segmented control instead of two
tinted tiles, the selected state no longer floods the option with the
primary colour, language rows are compact with outlined badges and a
primary check, option icons are 1rem, and panels use the radius tokens.

StatsBar: items are non-interactive articles, so drop the hover fill that
made a stat look pressed under the pointer.

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

packages/ui/components/StatsBar.wrn

@@ -287,14 +287,6 @@ component StatsBar {
       --item-accent: var(--wrn-color-danger);
     }
 
-    .wrn-stats-bar__item:hover {
-      background: var(--wrn-color-surface-soft);
-    }
-
-    .wrn-stats-bar[data-variant="solid"] .wrn-stats-bar__item:hover {
-      background: color-mix(in srgb, white 8%, transparent);
-    }
-
     .wrn-stats-bar__content {
       min-width: 0;
     }