Lift the selected tab and clipboard label above 4.5:1

Both drew small text in the raw accent, which misses the contrast floor on
a dark surface. They now blend the accent toward the text colour, as the
unselected tab already does.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

packages/ui/components/Tabs.wrn

@@ -277,7 +277,8 @@ component Tabs {
 
     .wrn-tabs__tab[aria-selected="true"] {
       background: var(--wrn-color-surface);
-      color: var(--tabs-accent);
+      /* Small text on the accent alone misses 4.5:1, so it blends toward the text colour. */
+      color: color-mix(in srgb, var(--tabs-accent) 72%, var(--wrn-color-text));
       box-shadow: var(--wrn-shadow-1);
     }