fix(ui): harden settings focus and semantics

lib/widgets/settings_section.dart

@@ -6,21 +6,19 @@ import 'expressive_button_group.dart';
 
 /// Standard settings-option title style.
 ///
-/// Matches Flutter's dense ListTile title size so custom controls and
-/// ordinary settings rows keep the same hierarchy. TV retains the larger
-/// body style used for D-pad readability at distance.
+/// Mobile uses Flutter's compact ListTile title size. Desktop and TV retain
+/// the larger body style used for pointer and D-pad readability.
 TextStyle? settingsOptionTitleStyle(BuildContext context) {
   final style = Theme.of(context).textTheme.bodyLarge;
-  return PlatformDetector.isTV() ? style : style?.copyWith(fontSize: 13);
+  return PlatformDetector.isMobile(context) ? style?.copyWith(fontSize: 13) : style;
 }
 
 /// Standard settings-row density, paired with [settingsOptionTitleStyle]:
-/// compact rows everywhere except TV, where full-height rows keep D-pad
-/// readability.
-bool settingsRowDense() => !PlatformDetector.isTV();
+/// compact on mobile and full-height on desktop and TV.
+bool settingsRowDense(BuildContext context) => PlatformDetector.isMobile(context);
 
-VisualDensity settingsRowVisualDensity() =>
-    settingsRowDense() ? const VisualDensity(vertical: -3) : VisualDensity.standard;
+VisualDensity settingsRowVisualDensity(BuildContext context) =>
+    settingsRowDense(context) ? const VisualDensity(vertical: -3) : VisualDensity.standard;
 
 class SettingsSectionHeader extends StatelessWidget {
   final String title;