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.Data/Models/ListEntity.cs

@@ -7,6 +7,7 @@ public sealed class ListEntity
     public required DateTime CreatedAt { get; init; }
     public string? WorkingDir { get; set; }
     public string DefaultCommitType { get; set; } = CommitTypeRegistry.DefaultType;
+    public int SortOrder { get; set; }
 
     // Navigation properties
     public ListConfigEntity? Config { get; set; }