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);
 		}

frontend/src/lib/components/PersonTypeSelector.svelte

@@ -16,6 +16,8 @@ let selected = $state<PersonType>(
 	untrack(() => (TYPES.includes(value as PersonType) ? (value as PersonType) : 'PERSON'))
 );
 
+let announcement = $state('');
+
 const labels: Record<PersonType, () => string> = {
 	PERSON: m.person_type_PERSON,
 	INSTITUTION: m.person_type_INSTITUTION,
@@ -25,15 +27,21 @@ const labels: Record<PersonType, () => string> = {
 
 function select(type: PersonType) {
 	selected = type;
+	announcement = m.a11y_type_changed({ type: labels[type]() });
 	onchange?.(type);
 }
 </script>
 
-<div role="radiogroup" class="grid grid-cols-2 gap-2 sm:grid-cols-4" use:radioGroupNav>
+<div
+	role="radiogroup"
+	class="grid grid-cols-2 gap-2 sm:grid-cols-4"
+	use:radioGroupNav={(v) => { if (TYPES.includes(v as PersonType)) select(v as PersonType); }}
+>
 	{#each TYPES as type (type)}
 		<button
 			type="button"
 			role="radio"
+			value={type}
 			aria-checked={selected === type}
 			tabindex={selected === type ? 0 : -1}
 			onclick={() => select(type)}
@@ -48,6 +56,4 @@ function select(type: PersonType) {
 
 <input type="hidden" name={name} value={selected} />
 
-<div class="sr-only" aria-live="polite">
+<div class="sr-only" aria-live="polite" aria-atomic="true">{announcement}</div>
-	{m.a11y_type_changed({ type: labels[selected]() })}
-</div>

frontend/src/lib/components/PersonTypeSelector.svelte.spec.ts

@@ -1,11 +1,23 @@
 import { describe, it, expect, afterEach } from 'vitest';
 import { cleanup, render } from 'vitest-browser-svelte';
+import { userEvent } from 'vitest/browser';
 
 import PersonTypeSelector from './PersonTypeSelector.svelte';
 
 afterEach(() => cleanup());
 
 describe('PersonTypeSelector', () => {
+	it('hidden input value updates when user navigates with ArrowRight', async () => {
+		const { container } = render(PersonTypeSelector, { value: 'PERSON' });
+		const hiddenInput = container.querySelector('input[type="hidden"]') as HTMLInputElement;
+		expect(hiddenInput.value).toBe('PERSON');
+
+		const personButton = container.querySelector('[aria-checked="true"]') as HTMLElement;
+		personButton.focus();
+		await userEvent.keyboard('{ArrowRight}');
+
+		expect(hiddenInput.value).toBe('INSTITUTION');
+	});
 	it('selected button uses semantic bg-primary and text-primary-fg classes', () => {
 		const { container } = render(PersonTypeSelector, { value: 'PERSON' });
 		const buttons = container.querySelectorAll('[role="radio"]');