test(briefwechsel): makePerson factory + per-row tile assertion

Consolidates the hansPerson / annaPerson fixture into a makePerson()
factory matching the makeDoc convention, adds an assertion that
the bilateral list renders one ConversationThumbnail tile per
document (catches a broken {#each} keying wired around the
DistributionBar), and decouples the DistributionBar aria-label
assertion from the German locale now that i18n lands via Paraglide.

Refs #305
Fixes @saraholt concerns 3 + 4 from PR review

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

frontend/src/routes/briefwechsel/page.svelte.spec.ts

@@ -30,20 +30,22 @@ const withPersons = {
 	filters: { ...baseData.filters, senderId: 'p1', receiverId: 'p2' }
 };
 
-const hansPerson = {
+const makePerson = (overrides: Record<string, unknown> = {}) => ({
 	id: 'p1',
 	firstName: 'Hans',
 	lastName: 'Müller',
 	personType: 'PERSON' as const,
-	displayName: 'Hans Müller'
+	displayName: 'Hans Müller',
-};
+	...overrides
-const annaPerson = {
+});
+
+const hansPerson = makePerson();
+const annaPerson = makePerson({
 	id: 'p2',
 	firstName: 'Anna',
 	lastName: 'Schmidt',
-	personType: 'PERSON' as const,
 	displayName: 'Anna Schmidt'
-};
+});
 
 const makeDoc = (overrides: Record<string, unknown> = {}) => ({
 	id: 'd1',
@@ -54,8 +56,15 @@ const makeDoc = (overrides: Record<string, unknown> = {}) => ({
 	location: 'Berlin',
 	metadataComplete: false,
 	scriptType: 'UNKNOWN' as const,
-	sender: hansPerson,
+	sender: makePerson(),
-	receivers: [annaPerson],
+	receivers: [
+		makePerson({
+			id: 'p2',
+			firstName: 'Anna',
+			lastName: 'Schmidt',
+			displayName: 'Anna Schmidt'
+		})
+	],
 	tags: [],
 	transcription: undefined,
 	filePath: undefined,
@@ -229,17 +238,33 @@ describe('Briefwechsel page – distribution bar', () => {
 			]
 		};
 		render(Page, { data });
-		const bar = document.querySelector('[role="img"][aria-label*="Briefverteilung"]');
+		const bar = document.querySelector('[role="img"]');
 		expect(bar).not.toBeNull();
-		expect(bar!.getAttribute('aria-label')).toContain('1 von Hans Müller');
+		const label = bar!.getAttribute('aria-label') ?? '';
-		expect(bar!.getAttribute('aria-label')).toContain('2 von Anna Schmidt');
+		expect(label).toContain('Hans Müller');
+		expect(label).toContain('Anna Schmidt');
+		expect(label).toMatch(/\b1\b/);
+		expect(label).toMatch(/\b2\b/);
 	});
 
 	it('does not render the DistributionBar in single-person mode', async () => {
 		render(Page, { data: { ...withSender, documents: [makeDoc()] } });
-		const bar = document.querySelector('[role="img"][aria-label*="Briefverteilung"]');
+		const bar = document.querySelector('[role="img"]');
 		expect(bar).toBeNull();
 	});
+
+	it('renders a ConversationThumbnail tile for each document in the list', async () => {
+		// A broken `{#each}` wiring in ConversationTimeline would silently stop
+		// rendering rows while the DistributionBar above it kept working. Assert
+		// the per-row tile so that class of regression is caught.
+		const data = {
+			...withPersons,
+			documents: [makeDoc({ id: 'd-a' }), makeDoc({ id: 'd-b' }), makeDoc({ id: 'd-c' })]
+		};
+		render(Page, { data });
+		const tiles = document.querySelectorAll('[data-testid="conv-thumb-tile"]');
+		expect(tiles).toHaveLength(3);
+	});
 });
 
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