fix(persons): keyboard navigation now updates PersonTypeSelector reactive state

radioGroupNav now accepts an onChange callback; PersonTypeSelector passes
select() as the callback so ArrowLeft/Right navigation updates the hidden
input value. aria-live region starts empty and announces only on user
interaction (fixes initial page-load announcement).

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

frontend/src/lib/actions/radioGroupNav.ts

@@ -1,4 +1,9 @@
-export function radioGroupNav(node: HTMLElement): { destroy: () => void } {
+export function radioGroupNav(
+	node: HTMLElement,
+	onChange?: (value: string) => void
+): { destroy: () => void; update: (onChange?: (value: string) => void) => void } {
+	let onChangeFn = onChange;
+
 	function getRadios(): HTMLElement[] {
 		return Array.from(node.querySelectorAll<HTMLElement>('[role="radio"]'));
 	}
@@ -16,11 +21,15 @@ export function radioGroupNav(node: HTMLElement): { destroy: () => void } {
 		radios[current].setAttribute('aria-checked', 'false');
 		radios[next].setAttribute('aria-checked', 'true');
 		radios[next].focus();
+		onChangeFn?.(radios[next].getAttribute('value') ?? '');
 	}
 
 	node.addEventListener('keydown', handleKeydown);
 
 	return {
+		update(newOnChange) {
+			onChangeFn = newOnChange;
+		},
 		destroy() {
 			node.removeEventListener('keydown', handleKeydown);
 		}