feat(ui): My Day actions, orphan-aware grouping, menu restructure

Pending UI work:
- My Day add/remove context actions on task rows (parent removal cascades to children)
- orphan-aware grouping: a child whose parent isn't in view renders as a top-level row, not an indented draft
- shell menu restructure (Worker / Repositories submenus); 'Finalize plan' action, drop 'Queue subtasks sequentially'
- notes editor refinements
- subtask-row hover tweak (Surface3, no transition)
- bump Avalonia 12.0.0 -> 12.0.4

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

@@ -35,6 +35,13 @@ public partial class DetailsIslandView : UserControl
         if (h <= 0) return;
         DetailBodyGrid.RowDefinitions[0].MaxHeight = h * 2.0 / 3.0;
         DetailBodyGrid.RowDefinitions[1].MinHeight = h / 3.0;
+        // The description sits in an Auto row, which measures its cell with
+        // infinite height — so the card's inner ScrollViewer thinks everything
+        // fits and never scrolls. Bounding the card itself gives that
+        // ScrollViewer a finite measure constraint so it engages once the
+        // content exceeds 2/3 of the island. (RowDefinition.MaxHeight above only
+        // clamps the drag and the final row height, not the measure constraint.)
+        DescriptionCard.MaxHeight = h * 2.0 / 3.0;
     }
 
     private void OnDataContextChanged(object? sender, EventArgs e)