refactor: move youtube primary subtitle config to youtube

src/config/definitions/domain-registry.test.ts

@@ -22,6 +22,7 @@ test('config option registry includes critical paths and has unique entries', ()
     'controller.enabled',
     'controller.scrollPixelsPerSecond',
     'startupWarmups.lowPowerMode',
+    'youtube.primarySubLanguages',
     'subtitleStyle.enableJlpt',
     'subtitleStyle.autoPauseVideoOnYomitanPopup',
     'ankiConnect.enabled',
@@ -43,6 +44,7 @@ test('config template sections include expected domains and unique keys', () =>
     'annotationWebsocket',
     'controller',
     'startupWarmups',
+    'youtube',
     'subtitleStyle',
     'ankiConnect',
     'yomitan',