Fix version selector focus ring (use focus-ring shortcut)

Was using undefined 'ring-ring' color, now uses consistent focus-ring shortcut

Author: JarvisInvestInsight

app/components/VersionSelector.vue

@@ -472,7 +472,7 @@ watch(
       type="button"
       aria-haspopup="listbox"
       :aria-expanded="isOpen"
-      class="flex items-center gap-1.5 text-fg-subtle font-mono text-sm hover:text-fg transition-[color] focus-visible:outline-none focus-visible:ring-2 focus-visible:ring-ring focus-visible:ring-offset-2 focus-visible:ring-offset-bg rounded"
+      class="flex items-center gap-1.5 text-fg-subtle font-mono text-sm hover:text-fg transition-[color] focus-ring rounded"
       @click="isOpen = !isOpen"
       @keydown="handleButtonKeydown"
     >