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/ViewModels/Islands/DetailsIslandViewModel.cs

@@ -840,6 +840,35 @@ public sealed partial class DetailsIslandViewModel : ViewModelBase
         CloseDetail?.Invoke();
     }
 
+    [RelayCommand]
+    private async System.Threading.Tasks.Task CommitSubtaskEditAsync(SubtaskRowViewModel? row)
+    {
+        if (row is null || !row.IsEditing) return;
+        row.IsEditing = false;
+
+        var title = row.Title?.Trim() ?? "";
+        await using var ctx = _dbFactory.CreateDbContext();
+        var repo = new SubtaskRepository(ctx);
+
+        // Emptying the text removes the step.
+        if (string.IsNullOrEmpty(title))
+        {
+            await repo.DeleteAsync(row.Id);
+            Subtasks.Remove(row);
+            return;
+        }
+
+        var subs = await repo.GetByTaskIdAsync(Task?.Id ?? "");
+        var entity = subs.FirstOrDefault(s => s.Id == row.Id);
+        if (entity is null) return;
+        if (entity.Title != title)
+        {
+            entity.Title = title;
+            await repo.UpdateAsync(entity);
+        }
+        row.Title = title;
+    }
+
     [RelayCommand]
     private async System.Threading.Tasks.Task AddSubtaskAsync()
     {
@@ -943,6 +972,7 @@ public sealed partial class SubtaskRowViewModel : ViewModelBase
     public required string Id { get; init; }
     [ObservableProperty] private string _title = "";
     [ObservableProperty] private bool _done;
+    [ObservableProperty] private bool _isEditing;
     [ObservableProperty] private ClaudeDo.Data.Models.TaskStatus _status;
     [ObservableProperty] private ClaudeDo.Data.Models.WorktreeState _worktreeState = ClaudeDo.Data.Models.WorktreeState.Active;
 }