test: cover four small primitives

RelationshipPill: label render, empty-string handling.
OverflowPillDisplay: +N rendering, +0 edge case, aria-hidden marker.
TimelineYAxis: max/0 labels, barAreaHeight inline style, zero handling.
TranscriptionSection: heading + textarea, initial-value hydration,
empty default.

11 tests across four small primitives.

Refs #496.

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

frontend/src/lib/person/relationship/RelationshipPill.svelte.test.ts

@@ -0,0 +1,21 @@
+import { describe, it, expect, afterEach } from 'vitest';
+import { cleanup, render } from 'vitest-browser-svelte';
+import { page } from 'vitest/browser';
+import RelationshipPill from './RelationshipPill.svelte';
+
+afterEach(cleanup);
+
+describe('RelationshipPill', () => {
+	it('renders the supplied label', async () => {
+		render(RelationshipPill, { props: { label: 'Vater' } });
+
+		await expect.element(page.getByText('Vater')).toBeVisible();
+	});
+
+	it('renders an empty string label without crashing', async () => {
+		render(RelationshipPill, { props: { label: '' } });
+
+		const span = document.querySelector('span');
+		expect(span).not.toBeNull();
+	});
+});