use Shad color scheme for workspace surfaces

lib/widgets/file_list_tile.dart

@@ -132,7 +132,7 @@ class _FileListTileState extends State<FileListTile> {
   @override
   Widget build(BuildContext context) {
     final theme = ShadTheme.of(context);
-    final isDark = theme.brightness == Brightness.dark;
+    final cs = theme.colorScheme;
     return ShadContextMenuRegion(
       items: [
         ShadContextMenuItem.inset(
@@ -210,20 +210,9 @@ class _FileListTileState extends State<FileListTile> {
           padding: const EdgeInsets.symmetric(horizontal: 12),
           decoration: BoxDecoration(
             color: widget.isSelected
-                ? (isDark
-                      ? theme.colorScheme.primary.withAlpha(30)
-                      : theme.colorScheme.primary.withAlpha(15))
-                : (isDark
-                      ? Colors.white.withAlpha(3)
-                      : Colors.black.withAlpha(2)),
-            border: Border(
-              bottom: BorderSide(
-                color: isDark
-                    ? Colors.white.withAlpha(10)
-                    : Colors.black.withAlpha(8),
-                width: 0.5,
-              ),
-            ),
+                ? cs.primary.withValues(alpha: 0.14)
+                : cs.card,
+            border: Border(bottom: BorderSide(color: cs.border, width: 0.5)),
           ),
           child: Row(
             children: [

lib/widgets/sort_menu.dart

@@ -18,21 +18,13 @@ class SortMenu extends StatelessWidget {
 
   @override
   Widget build(BuildContext context) {
-    final theme = ShadTheme.of(context);
-    final cs = theme.colorScheme;
-    final isDark = theme.brightness == Brightness.dark;
+    final cs = ShadTheme.of(context).colorScheme;
     return Container(
       height: 36,
       decoration: BoxDecoration(
-        color: isDark
-            ? cs.secondary.withValues(alpha: 0.88)
-            : Colors.white.withValues(alpha: 0.46),
+        color: cs.secondary,
         borderRadius: BorderRadius.circular(10),
-        border: Border.all(
-          color: isDark
-              ? cs.border.withValues(alpha: 0.9)
-              : Colors.white.withValues(alpha: 0.54),
-        ),
+        border: Border.all(color: cs.border),
       ),
       child: Row(
         mainAxisSize: MainAxisSize.min,