fix(ui): app-bar tab chip strips scroll instead of overflowing

Shared TabChipStrip replaces the plain Rows in libraries/downloads/live
TV app bars (and live TV's hand-rolled scroll wrapper); chips center
themselves on focus so d-pad reaches off-screen tabs.

lib/focus/focusable_chip_mixin.dart

@@ -3,6 +3,7 @@ import 'dart:async';
 import 'package:flutter/material.dart';
 import 'package:flutter/services.dart';
 
+import '../utils/scroll_utils.dart';
 import 'dpad_navigator.dart';
 import 'key_event_utils.dart';
 
@@ -86,6 +87,10 @@ mixin FocusableChipStateMixin<T extends StatefulWidget> on State<T> {
   void _onFocusChange() {
     if (mounted) {
       setState(() => _isFocused = focusNode.hasFocus);
+      // Same convention as FocusableTileStateMixin: a chip inside a
+      // scrollable strip (TabChipStrip, filter bars) reveals itself on
+      // focus; a no-op when no ancestor scrollable exists.
+      if (focusNode.hasFocus) scrollContextToCenter(context);
     }
   }
 

lib/screens/downloads/downloads_screen.dart

@@ -12,6 +12,7 @@ import '../../services/music/music_playback_service.dart';
 import '../../theme/mono_tokens.dart';
 import '../../utils/music_navigation.dart';
 import '../../widgets/app_icon.dart';
+import '../../widgets/focusable_tab_chip.dart';
 import '../../widgets/music/mini_player.dart';
 import '../../widgets/music/track_row.dart';
 import '../../services/settings_service.dart';
@@ -114,7 +115,7 @@ class DownloadsScreenState extends State<DownloadsScreen>
   Widget _buildAppBarTitle() {
     // On desktop/TV with side nav, show tabs in app bar
     if (PlatformDetector.shouldUseSideNavigation(context)) {
-      return Row(
+      return TabChipStrip(
         children: [
           _buildTabChip(t.downloads.manage, 0),
           const SizedBox(width: 8),

lib/screens/libraries/libraries_screen.dart

@@ -24,6 +24,7 @@ import '../../utils/content_utils.dart';
 import '../../widgets/app_menu.dart';
 import '../../widgets/backend_badge.dart';
 import '../../widgets/desktop_app_bar.dart';
+import '../../widgets/focusable_tab_chip.dart';
 import '../../widgets/library_management_sheet.dart';
 import '../../services/storage_service.dart';
 import '../../mixins/refreshable.dart';
@@ -681,8 +682,7 @@ class _LibrariesScreenState extends State<LibrariesScreen>
 
     // On desktop/TV with side nav, show tabs in app bar (library name is in side nav)
     if (PlatformDetector.shouldUseSideNavigation(context)) {
-      return Row(
-        mainAxisSize: .min,
+      return TabChipStrip(
         children: [
           for (int i = 0; i < _visibleTabs.length; i++) ...[
             if (i > 0) const SizedBox(width: 8),

lib/screens/livetv/live_tv_screen.dart

@@ -23,6 +23,7 @@ import '../../utils/desktop_window_padding.dart';
 import '../../utils/platform_detector.dart';
 import '../../utils/snackbar_helper.dart';
 import '../../widgets/app_icon.dart';
+import '../../widgets/focusable_tab_chip.dart';
 import '../../widgets/overlay_sheet.dart';
 import 'reorder_favorites_sheet.dart';
 import 'tabs/guide_tab.dart';
@@ -549,7 +550,7 @@ class _LiveTvScreenState extends State<LiveTvScreen>
     final isRecordings = _currentTab == LiveTvTab.recordings;
     return Scaffold(
       appBar: AppBar(
-        title: useSideNav ? Row(children: _buildTabChipItems()) : Text(t.liveTv.title),
+        title: useSideNav ? TabChipStrip(children: _buildTabChipItems()) : Text(t.liveTv.title),
         actions: DesktopAppBarHelper.buildAdjustedActions([
           FocusableActionBar(
             key: _actionBarKey,
@@ -646,10 +647,7 @@ class _LiveTvScreenState extends State<LiveTvScreen>
           Container(
             padding: const EdgeInsets.symmetric(horizontal: 16, vertical: 8),
             alignment: .centerLeft,
-            child: SingleChildScrollView(
-              scrollDirection: Axis.horizontal,
-              child: Row(children: _buildTabChipItems()),
-            ),
+            child: TabChipStrip(children: _buildTabChipItems()),
           ),
         Expanded(
           child: TabBarView(

lib/widgets/focusable_tab_chip.dart

@@ -5,6 +5,27 @@ import '../focus/input_mode_tracker.dart';
 import '../utils/platform_detector.dart';
 import 'focus_builders.dart';
 
+/// Horizontally scrollable host for a row of [FocusableTabChip]s.
+///
+/// App-bar titles and header rows give the strip a bounded width; a plain
+/// Row overflows it on narrow windows (visible as the striped overflow
+/// indicator). The strip shrink-wraps like `mainAxisSize: min` and scrolls
+/// instead. D-pad stays correct: chips center themselves on focus via the
+/// chip mixin, so LEFT/RIGHT reaches off-screen tabs.
+class TabChipStrip extends StatelessWidget {
+  final List<Widget> children;
+
+  const TabChipStrip({super.key, required this.children});
+
+  @override
+  Widget build(BuildContext context) {
+    return SingleChildScrollView(
+      scrollDirection: Axis.horizontal,
+      child: Row(mainAxisSize: .min, children: children),
+    );
+  }
+}
+
 /// A focusable tab chip that shows a color change when focused or selected.
 ///
 /// Used for tab navigation in LibrariesScreen. Handles: