fix(nav): hide active sidebar background during focus

lib/widgets/side_navigation_rail.dart

@@ -60,6 +60,7 @@ class NavigationRailItem extends StatelessWidget {
   final BorderRadius borderRadius;
   final double iconSize;
   final double horizontalPadding;
+  final bool suppressSelectedBackground;
 
   /// Called when RIGHT arrow is pressed to navigate to content area.
   final VoidCallback? onNavigateRight;
@@ -79,12 +80,14 @@ class NavigationRailItem extends StatelessWidget {
     this.borderRadius = const BorderRadius.all(Radius.circular(12)),
     this.iconSize = 22,
     this.horizontalPadding = 17,
+    this.suppressSelectedBackground = false,
     this.onNavigateRight,
   });
 
   @override
   Widget build(BuildContext context) {
     final t = tokens(context);
+    final showSelectedBackground = isSelected && !suppressSelectedBackground;
 
     return Focus(
       focusNode: focusNode,
@@ -111,9 +114,8 @@ class NavigationRailItem extends StatelessWidget {
             decoration: BoxDecoration(
               color: () {
                 if (isCollapsed) return isFocused ? t.text.withValues(alpha: 0.12) : null;
-                if (isSelected && isFocused) return t.text.withValues(alpha: 0.15);
-                if (isSelected) return t.text.withValues(alpha: 0.1);
-                if (isFocused) return t.text.withValues(alpha: 0.12);
+                if (isFocused) return t.text.withValues(alpha: showSelectedBackground ? 0.15 : 0.12);
+                if (showSelectedBackground) return t.text.withValues(alpha: 0.1);
                 return null;
               }(),
               borderRadius: borderRadius,
@@ -792,6 +794,7 @@ class SideNavigationRailState extends State<SideNavigationRail> with MountedSetS
       focusNode: focusNode,
       autofocus: autofocus,
       horizontalPadding: itemHorizontalPadding,
+      suppressSelectedBackground: widget.isSidebarFocused,
       onNavigateRight: widget.onNavigateToContent,
     );
   }
@@ -858,6 +861,7 @@ class SideNavigationRailState extends State<SideNavigationRail> with MountedSetS
     final isLoading = librariesProvider.isLoading;
     final isLibrariesSelected = widget.selectedTab == NavigationTabId.libraries && widget.selectedLibraryKey == null;
     final isLibrariesFocused = _focusTracker.isFocused(_kLibraries);
+    final showLibrariesSelectedBackground = isLibrariesSelected && !widget.isSidebarFocused;
     final allEmpty = visibleRows.isEmpty && hiddenLibraryCount == 0;
 
     return Column(
@@ -894,7 +898,7 @@ class SideNavigationRailState extends State<SideNavigationRail> with MountedSetS
                 decoration: BoxDecoration(
                   color: () {
                     if (isCollapsed) return isLibrariesFocused ? t.text.withValues(alpha: 0.08) : null;
-                    if (isLibrariesSelected) return t.text.withValues(alpha: 0.1);
+                    if (showLibrariesSelectedBackground) return t.text.withValues(alpha: 0.1);
                     if (isLibrariesFocused) return t.text.withValues(alpha: 0.08);
                     return null;
                   }(),
@@ -1190,6 +1194,7 @@ class SideNavigationRailState extends State<SideNavigationRail> with MountedSetS
         focusNode: focusNode,
         borderRadius: BorderRadius.circular(tokens(context).radiusSm),
         iconSize: 18,
+        suppressSelectedBackground: widget.isSidebarFocused,
         onNavigateRight: widget.onNavigateToContent,
       ),
     );

test/widgets/side_navigation_rail_test.dart

@@ -58,6 +58,58 @@ Future<void> _press(WidgetTester tester, LogicalKeyboardKey key) async {
   await tester.pumpAndSettle();
 }
 
+BoxDecoration? _railItemDecoration(WidgetTester tester, Finder item) {
+  return tester.widget<Container>(find.descendant(of: item, matching: find.byType(Container)).first).decoration
+      as BoxDecoration?;
+}
+
+Future<void> _pumpBasicRail(
+  WidgetTester tester, {
+  GlobalKey<SideNavigationRailState>? sideNavKey,
+  bool isSidebarFocused = false,
+  bool alwaysExpanded = false,
+}) async {
+  await SettingsService.getInstance();
+
+  final librariesProvider = LibrariesProvider();
+  addTearDown(librariesProvider.dispose);
+
+  final hiddenLibrariesProvider = HiddenLibrariesProvider();
+  await hiddenLibrariesProvider.ensureInitialized();
+  addTearDown(hiddenLibrariesProvider.dispose);
+
+  final manager = MultiServerManager();
+  final aggregation = DataAggregationService(manager);
+  final multiServerProvider = MultiServerProvider(manager, aggregation);
+  addTearDown(multiServerProvider.dispose);
+
+  await tester.pumpWidget(
+    TranslationProvider(
+      child: MultiProvider(
+        providers: [
+          ChangeNotifierProvider<LibrariesProvider>.value(value: librariesProvider),
+          ChangeNotifierProvider<HiddenLibrariesProvider>.value(value: hiddenLibrariesProvider),
+          ChangeNotifierProvider<MultiServerProvider>.value(value: multiServerProvider),
+        ],
+        child: MaterialApp(
+          theme: ThemeData(extensions: const [_testTokens]),
+          home: Scaffold(
+            body: SideNavigationRail(
+              key: sideNavKey,
+              selectedTab: NavigationTabId.discover,
+              isSidebarFocused: isSidebarFocused,
+              alwaysExpanded: alwaysExpanded,
+              onDestinationSelected: (_) {},
+              onLibrarySelected: (_) {},
+            ),
+          ),
+        ),
+      ),
+    ),
+  );
+  await tester.pumpAndSettle();
+}
+
 void main() {
   TestWidgetsFlutterBinding.ensureInitialized();
 
@@ -177,6 +229,25 @@ void main() {
     expect(surfaceOpacity.opacity, 0.0);
   });
 
+  testWidgets('expanded rail keeps selected background outside sidebar keyboard focus', (tester) async {
+    await _pumpBasicRail(tester, alwaysExpanded: true);
+
+    final selectedItem = find.byType(NavigationRailItem).first;
+    expect(_railItemDecoration(tester, selectedItem)?.color, _testTokens.text.withValues(alpha: 0.1));
+  });
+
+  testWidgets('D-pad sidebar focus hides selected item background after focus moves', (tester) async {
+    final sideNavKey = GlobalKey<SideNavigationRailState>();
+    await _pumpBasicRail(tester, sideNavKey: sideNavKey, isSidebarFocused: true, alwaysExpanded: true);
+
+    sideNavKey.currentState!.focusActiveItem();
+    await tester.pumpAndSettle();
+    await _press(tester, LogicalKeyboardKey.arrowDown);
+
+    final selectedItem = find.byType(NavigationRailItem).first;
+    expect(_railItemDecoration(tester, selectedItem)?.color, isNull);
+  });
+
   testWidgets('reports interaction expansion for shell content push', (tester) async {
     await SettingsService.getInstance();