fix: stabilize grid column count when alpha bar shows

lib/screens/libraries/tabs/library_browse_tab.dart

@@ -1248,7 +1248,7 @@ class _LibraryBrowseTabState extends BaseLibraryTabState<PlexMetadata, LibraryBr
   static const double _gridTopPaddingPhone = _chipsBarHeight;
 
   /// Width of the alpha jump bar widget
-  static const double _alphaJumpBarWidth = 28.0;
+  static const double _alphaJumpBarWidth = 20.0;
 
   /// Builds either a sliver list or sliver grid based on the view mode
   Widget _buildItemsSliver(BuildContext context, SettingsProvider settingsProvider) {
@@ -1277,12 +1277,18 @@ class _LibraryBrowseTabState extends BaseLibraryTabState<PlexMetadata, LibraryBr
       // Use 16:9 aspect ratio when browsing episodes with episode thumbnail mode
       final useWideRatio =
           _selectedGrouping == 'episodes' && settingsProvider.episodePosterMode == EpisodePosterMode.episodeThumbnail;
-      final maxExtent = GridSizeCalculator.getMaxCrossAxisExtent(context, settingsProvider.libraryDensity);
+      final baseMaxExtent = GridSizeCalculator.getMaxCrossAxisExtent(context, settingsProvider.libraryDensity);
+      final effectiveMaxExtent = useWideRatio ? baseMaxExtent * 1.8 : baseMaxExtent;
+      final hasAlphaBarReservation = rightPadding > 8.0;
       return SliverPadding(
         padding: EdgeInsets.fromLTRB(8, topPadding, rightPadding, 8),
         sliver: SliverLayoutBuilder(
           builder: (context, constraints) {
-            final columnCount = GridSizeCalculator.getColumnCount(constraints.crossAxisExtent, maxExtent);
+            // Compute column count from the width the grid would have without the alpha
+            // bar's reservation, so toggling the bar doesn't repack the grid into one
+            // fewer column and blow up poster size.
+            final baselineWidth = constraints.crossAxisExtent + (rightPadding - 8.0);
+            final columnCount = GridSizeCalculator.getColumnCount(baselineWidth, effectiveMaxExtent);
             // Cache grid metrics for alpha jump bar scroll calculations
             _lastCrossAxisExtent = constraints.crossAxisExtent;
             _currentColumnCount = columnCount;
@@ -1291,6 +1297,7 @@ class _LibraryBrowseTabState extends BaseLibraryTabState<PlexMetadata, LibraryBr
                 context: context,
                 density: settingsProvider.libraryDensity,
                 useWideAspectRatio: useWideRatio,
+                maxCrossAxisExtentOverride: hasAlphaBarReservation ? constraints.crossAxisExtent / columnCount : null,
               ),
               itemCount: itemCount,
               itemBuilder: (context, index) => _buildMediaCardItem(

lib/widgets/media_grid_delegate.dart

@@ -10,26 +10,34 @@ class MediaGridDelegate {
   /// Uses [GridSizeCalculator.getMaxCrossAxisExtent] by default.
   /// Set [usePaddingAware] to true to use [GridSizeCalculator.getMaxCrossAxisExtentWithPadding] instead.
   /// Set [useWideAspectRatio] to true to use 16:9 aspect ratio for episode thumbnails.
+  /// Pass [maxCrossAxisExtentOverride] to bypass the calculator and the wide-aspect multiplier —
+  /// the caller is then responsible for providing a fully-resolved per-cell width.
   static SliverGridDelegateWithMaxCrossAxisExtent createDelegate({
     required BuildContext context,
     required int density,
     bool usePaddingAware = false,
     double horizontalPadding = 16,
     bool useWideAspectRatio = false,
+    double? maxCrossAxisExtentOverride,
   }) {
-    var maxCrossAxisExtent = usePaddingAware
-        ? GridSizeCalculator.getMaxCrossAxisExtentWithPadding(context, density, horizontalPadding)
-        : GridSizeCalculator.getMaxCrossAxisExtent(context, density);
-
     final aspectRatio = useWideAspectRatio
         ? GridLayoutConstants.episodeGridCellAspectRatio
         : GridLayoutConstants.posterAspectRatio;
 
+    double maxCrossAxisExtent;
+    if (maxCrossAxisExtentOverride != null) {
+      maxCrossAxisExtent = maxCrossAxisExtentOverride;
+    } else {
+      maxCrossAxisExtent = usePaddingAware
+          ? GridSizeCalculator.getMaxCrossAxisExtentWithPadding(context, density, horizontalPadding)
+          : GridSizeCalculator.getMaxCrossAxisExtent(context, density);
+
       // For wide aspect ratio (16:9), increase max extent so items are larger
       // and there are fewer per row (roughly 1.8x wider to maintain similar visual area)
       if (useWideAspectRatio) {
         maxCrossAxisExtent *= 1.8;
       }
+    }
 
     return SliverGridDelegateWithMaxCrossAxisExtent(
       maxCrossAxisExtent: maxCrossAxisExtent,