fix(ui): live-refresh child rows on parent planning transitions

Finalize/Discard broadcast only the parent's TaskUpdated; the delta path
updated the parent row but never recomputed child-derived flags or dropped
discarded children, so subtasks stayed "Draft" after finalize and deleted
rows lingered after discard until a manual reload. Reconcile the whole
list when the updated task is (or owns) a planning subtree.

src/ClaudeDo.Ui/ViewModels/Islands/TasksIslandViewModel.cs

@@ -151,6 +151,18 @@ public sealed partial class TasksIslandViewModel : ViewModelBase, IDisposable
                 .Include(t => t.Worktree)
                 .FirstOrDefaultAsync(t => t.Id == taskId);
 
+            // A parent transition (finalize/discard) broadcasts only the parent's id, but it
+            // changes its children's derived state — finalize flips them Draft→Planned, discard
+            // deletes them. The delta path below only touches the parent row and never recomputes
+            // the child-derived flags (ParentFinalized, HasPlanningChildren) nor drops deleted
+            // children, so reconcile the whole list when the updated task is (or owns) a subtree.
+            if (entity is not null &&
+                (entity.PlanningPhase != PlanningPhase.None || Items.Any(r => r.ParentTaskId == entity.Id)))
+            {
+                LoadForList(list);
+                return;
+            }
+
             var existing = Items.FirstOrDefault(r => r.Id == taskId);
 
             if (entity is null)