fix(kanban): column headers follow rounded theme corners

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

frontend/src/features/triage/TasksView.tsx

@@ -2134,7 +2134,7 @@ export const TasksView: React.FC<TasksViewProps> = ({
                     if (dragOverKanbanCol === col.id) setDragOverKanbanCol(null);
                   }}
                   onDrop={(e) => handleDropOnKanbanCol(e, col.id)}
-                  className={`bg-canvas border border-border flex flex-col min-h-[420px] transition-all ${
+                  className={`bg-canvas border border-border flex flex-col min-h-[420px] overflow-hidden transition-all ${
                     dragOverKanbanCol === col.id ? 'ring-2 ring-accent/60 bg-accent/5' : ''
                   }`}
                 >