feat(ui): list reordering, quick actions, and resizable modals

- Drag-to-reorder user lists in the sidebar, persisted via a new
  list sort_order column (AddListSortOrder migration, backfilled by
  creation time) and ListRepository.ReorderAsync
- "Open in Explorer" / "Open in Terminal" context-menu actions on lists
- "Clear all completed" button on the Tasks island
- Inline-edit subtask titles (empty text deletes the step) and
  click-to-copy task ID in the Details island
- Make modal and planning windows resizable (BorderOnly decorations
  with min sizes) instead of fixed-size borderless

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

src/ClaudeDo.Ui/Views/Islands/ListsIslandView.axaml.cs

@@ -1,9 +1,11 @@
 using System.Linq;
 using Avalonia;
 using Avalonia.Controls;
+using Avalonia.Input;
 using Avalonia.Interactivity;
 using Avalonia.Layout;
 using Avalonia.Media;
+using Avalonia.VisualTree;
 using ClaudeDo.Ui.ViewModels;
 using ClaudeDo.Ui.ViewModels.Islands;
 using ClaudeDo.Ui.ViewModels.Modals;
@@ -13,9 +15,13 @@ namespace ClaudeDo.Ui.Views.Islands;
 
 public partial class ListsIslandView : UserControl
 {
+    private static readonly DataFormat<string> ListRowFormat =
+        DataFormat.CreateStringApplicationFormat("claudedo-list-row");
+
     public ListsIslandView()
     {
         InitializeComponent();
+        AddHandler(PointerPressedEvent, OnTunnelPointerPressed, RoutingStrategies.Tunnel);
         DataContextChanged += (_, _) =>
         {
             if (DataContext is ListsIslandViewModel vm)
@@ -84,6 +90,127 @@ public partial class ListsIslandView : UserControl
             vm.SelectCommand.Execute(item);
     }
 
+    private async void OnTunnelPointerPressed(object? sender, PointerPressedEventArgs e)
+    {
+        if (DataContext is not ListsIslandViewModel vm) return;
+        if (e.Source is not Visual src) return;
+
+        var border = FindListItemBorder(src);
+        if (border?.DataContext is not ListNavItemViewModel row || row.Kind != ListKind.User) return;
+        if (!e.GetCurrentPoint(border).Properties.IsLeftButtonPressed) return;
+
+        // Double-click opens the list's settings instead of starting a drag. Handled here
+        // because DoDragDropAsync captures the pointer and would swallow a DoubleTapped event.
+        if (e.ClickCount == 2)
+        {
+            vm.OpenListSettingsCommand.Execute(row);
+            return;
+        }
+
+        // Select now so the right pane updates whether the gesture becomes a click or a drag
+        // (the Tapped handler doesn't fire once DoDragDropAsync captures the pointer).
+        vm.SelectCommand.Execute(row);
+
+        var data = new DataTransfer();
+        data.Add(DataTransferItem.Create(ListRowFormat, row.Id));
+        try
+        {
+            await DragDrop.DoDragDropAsync(e, data, DragDropEffects.Move);
+        }
+        finally
+        {
+            vm.ClearDropHints();
+        }
+    }
+
+    private void OnListDragOver(object? sender, DragEventArgs e)
+    {
+        if (DataContext is not ListsIslandViewModel vm) { e.DragEffects = DragDropEffects.None; return; }
+        if (!e.DataTransfer?.Contains(ListRowFormat) ?? true)
+        {
+            e.DragEffects = DragDropEffects.None;
+            vm.ClearDropHints();
+            return;
+        }
+        if (sender is not Border b || b.DataContext is not ListNavItemViewModel target || target.Kind != ListKind.User)
+        {
+            e.DragEffects = DragDropEffects.None;
+            vm.ClearDropHints();
+            return;
+        }
+
+        var sourceId = e.DataTransfer?.TryGetValue(ListRowFormat);
+        if (string.IsNullOrEmpty(sourceId) || sourceId == target.Id)
+        {
+            e.DragEffects = DragDropEffects.None;
+            vm.ClearDropHints();
+            return;
+        }
+
+        var placeBelow = e.GetPosition(b).Y > b.Bounds.Height / 2;
+
+        // Canonicalize: "drop below X" == "drop above X+1". Only the last row shows a below-line.
+        ListNavItemViewModel hintRow = target;
+        bool hintBelow = false;
+        if (placeBelow)
+        {
+            var next = FindNextUserList(vm, target);
+            if (next is not null) { hintRow = next; hintBelow = false; }
+            else { hintRow = target; hintBelow = true; }
+        }
+
+        if (hintRow.Id == sourceId)
+        {
+            e.DragEffects = DragDropEffects.None;
+            vm.ClearDropHints();
+            return;
+        }
+
+        vm.SetDropHint(hintRow, hintBelow);
+        e.DragEffects = DragDropEffects.Move;
+    }
+
+    private async void OnListDrop(object? sender, DragEventArgs e)
+    {
+        if (DataContext is not ListsIslandViewModel vm) return;
+        try
+        {
+            if (sender is not Border b || b.DataContext is not ListNavItemViewModel target || target.Kind != ListKind.User) return;
+
+            var sourceId = e.DataTransfer?.TryGetValue(ListRowFormat);
+            if (string.IsNullOrEmpty(sourceId) || sourceId == target.Id) return;
+
+            var source = vm.UserLists.FirstOrDefault(r => r.Id == sourceId);
+            if (source is null) return;
+
+            var placeBelow = e.GetPosition(b).Y > b.Bounds.Height / 2;
+            vm.ClearDropHints();
+            await vm.ReorderAsync(source, target, placeBelow);
+        }
+        catch
+        {
+            vm.ClearDropHints();
+            throw;
+        }
+    }
+
+    private static Border? FindListItemBorder(Visual? v)
+    {
+        while (v is not null)
+        {
+            if (v is Border b && b.Classes.Contains("list-item")) return b;
+            v = v.GetVisualParent();
+        }
+        return null;
+    }
+
+    private static ListNavItemViewModel? FindNextUserList(ListsIslandViewModel vm, ListNavItemViewModel row)
+    {
+        var idx = vm.UserLists.IndexOf(row);
+        if (idx < 0) return null;
+        return idx + 1 < vm.UserLists.Count ? vm.UserLists[idx + 1] : null;
+    }
+
     private async System.Threading.Tasks.Task ShowSettingsAsync(SettingsModalViewModel settingsVm)
     {
         var owner = TopLevel.GetTopLevel(this) as Window;