test(actions): add defaultPrevented coverage for clickOutside (#195)

The action already checks event.defaultPrevented before dispatching
clickoutside, but that branch had no test. Add the missing case and
add a one-line comment explaining why capture phase is used.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

frontend/src/lib/actions/clickOutside.ts

@@ -5,6 +5,7 @@ export function clickOutside(node: HTMLElement): { destroy: () => void } {
 		}
 	}
 
+	// Capture phase (true) ensures this fires before any child stopPropagation() calls.
 	document.addEventListener('click', handleClick, true);
 
 	return {