Fix: Explanation card visible + visual divider between 2/3 and 1/3

- exerciseType prop for correct explanation lookup (was using title)
- Vertical divider line between work area and native helper
- Cyan-tinted explanation card with lightbulb icon
- Padding between sections (pr-6 / pl-6 around divider)
- Explanation card has distinct background for visibility

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

studio-v2/app/learn/[unitId]/match/page.tsx

@@ -124,9 +124,9 @@ export default function MatchPage() {
   return (
     <ExerciseLayout
       title={t('match')}
+      exerciseType="match"
       onBack={() => router.push('/learn')}
       progress={{ current: matchedTotal, total: totalPairs }}
-      exerciseExplanation={undefined}
       nativeHelper={nativePanel}
       score={
         <div className={`text-xs ${isDark ? 'text-white/50' : 'text-slate-500'}`}>