Fix: Cast entry to avoid TypeScript 'never' inference

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

studio-v2/lib/NativeLanguageContext.tsx

@@ -39,7 +39,8 @@ export function NativeLanguageProvider({ children }: { children: React.ReactNode
   const t = useCallback((key: ExerciseKey): string => {
     const entry = exerciseT[key]
     if (!entry) return key
-    return (entry as Record<string, string>)[nativeLang] || entry.en || entry.de || key
+    const e = entry as Record<string, string>
+    return e[nativeLang] || e['en'] || e['de'] || key
   }, [nativeLang])
 
   const wordInNative = useCallback((translations?: Record<string, any>): string => {