fix(ui): refine narrow layouts and enable tab swipes

ui/flutter/lib/shared/widgets/file_tree_view.dart

@@ -69,6 +69,7 @@ class FileTreeView<T> extends StatefulWidget {
     this.rowHeight = _treeRowHeight,
     this.contentTextStyle,
     this.iconSize = 18,
+    this.initialExpandedDepth,
   });
 
   final List<FileTreeItem<T>> items;
@@ -85,6 +86,9 @@ class FileTreeView<T> extends StatefulWidget {
   final TextStyle? contentTextStyle;
   final double iconSize;
 
+  /// Number of directory levels initially expanded; null expands all levels.
+  final int? initialExpandedDepth;
+
   @override
   State<FileTreeView<T>> createState() => _FileTreeViewState<T>();
 }
@@ -109,7 +113,7 @@ class _FileTreeViewState<T> extends State<FileTreeView<T>> with SingleTickerProv
   @override
   void initState() {
     super.initState();
-    _nodes = _buildTree(widget.items);
+    _nodes = _buildTree(widget.items, expandedDepth: widget.initialExpandedDepth);
     _allFoldersExpanded = _foldersAreExpanded(_nodes);
     _transitionController = AnimationController(vsync: this, duration: _treeTransitionDuration, value: 1)
       ..addStatusListener(_onTransitionStatus);
@@ -830,8 +834,10 @@ class _BuildNode<T> {
 
   int get size => item?.size ?? children.fold<int>(0, (sum, child) => sum + child.size);
 
-  TreeItemNode<FileTreeNode<T>> toTreeItem() {
-    final childItems = children.map((child) => child.toTreeItem()).toList(growable: false);
+  TreeItemNode<FileTreeNode<T>> toTreeItem({int? expandedDepth, int depth = 0}) {
+    final childItems = children
+        .map((child) => child.toTreeItem(expandedDepth: expandedDepth, depth: depth + 1))
+        .toList(growable: false);
     final leaves = item == null ? [for (final child in childItems) ...child.data.leafItems] : <FileTreeItem<T>>[item!];
     return TreeItemNode(
       data: FileTreeNode(
@@ -842,13 +848,13 @@ class _BuildNode<T> {
         originalIndex: originalIndex,
         item: item,
       ),
-      expanded: true,
+      expanded: expandedDepth == null || depth < expandedDepth,
       children: childItems,
     );
   }
 }
 
-List<TreeNode<FileTreeNode<T>>> _buildTree<T>(List<FileTreeItem<T>> items) {
+List<TreeNode<FileTreeNode<T>>> _buildTree<T>(List<FileTreeItem<T>> items, {int? expandedDepth}) {
   final root = <_BuildNode<T>>[];
   final folders = <String, _BuildNode<T>>{};
   var originalIndex = 0;
@@ -885,7 +891,7 @@ List<TreeNode<FileTreeNode<T>>> _buildTree<T>(List<FileTreeItem<T>> items) {
     }
   }
 
-  return root.map((node) => node.toTreeItem()).toList(growable: false);
+  return root.map((node) => node.toTreeItem(expandedDepth: expandedDepth)).toList(growable: false);
 }
 
 List<String> _visibleNodeKeysInOrder<T>(List<TreeNode<FileTreeNode<T>>> nodes) {