feat(persons): add radioGroupNav action for keyboard navigation in type selector

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

frontend/src/lib/actions/radioGroupNav.ts

@@ -0,0 +1,28 @@
+export function radioGroupNav(node: HTMLElement): { destroy: () => void } {
+	function getRadios(): HTMLElement[] {
+		return Array.from(node.querySelectorAll<HTMLElement>('[role="radio"]'));
+	}
+
+	function handleKeydown(event: KeyboardEvent) {
+		if (event.key !== 'ArrowRight' && event.key !== 'ArrowLeft') return;
+
+		const radios = getRadios();
+		const current = radios.indexOf(document.activeElement as HTMLElement);
+		if (current === -1) return;
+
+		const delta = event.key === 'ArrowRight' ? 1 : -1;
+		const next = (current + delta + radios.length) % radios.length;
+
+		radios[current].setAttribute('aria-checked', 'false');
+		radios[next].setAttribute('aria-checked', 'true');
+		radios[next].focus();
+	}
+
+	node.addEventListener('keydown', handleKeydown);
+
+	return {
+		destroy() {
+			node.removeEventListener('keydown', handleKeydown);
+		}
+	};
+}