test(briefwechsel): cover DistributionBar and fix Person fixture shape

Adds two new assertions for the extracted DistributionBar — it must
appear in bilateral mode and stay hidden in single-person mode — and
repairs the shared makeDoc fixture: the embedded Person now carries
personType + displayName so the fixture matches the regenerated
Document schema without TypeScript complaints.

Refs #305

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

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

@@ -30,6 +30,21 @@ const withPersons = {
 	filters: { ...baseData.filters, senderId: 'p1', receiverId: 'p2' }
 };
 
+const hansPerson = {
+	id: 'p1',
+	firstName: 'Hans',
+	lastName: 'Müller',
+	personType: 'PERSON' as const,
+	displayName: 'Hans Müller'
+};
+const annaPerson = {
+	id: 'p2',
+	firstName: 'Anna',
+	lastName: 'Schmidt',
+	personType: 'PERSON' as const,
+	displayName: 'Anna Schmidt'
+};
+
 const makeDoc = (overrides: Record<string, unknown> = {}) => ({
 	id: 'd1',
 	title: 'Testbrief',
@@ -39,8 +54,8 @@ const makeDoc = (overrides: Record<string, unknown> = {}) => ({
 	location: 'Berlin',
 	metadataComplete: false,
 	scriptType: 'UNKNOWN' as const,
-	sender: { id: 'p1', firstName: 'Hans', lastName: 'Müller' },
+	sender: hansPerson,
-	receivers: [{ id: 'p2', firstName: 'Anna', lastName: 'Schmidt' }],
+	receivers: [annaPerson],
 	tags: [],
 	transcription: undefined,
 	filePath: undefined,
@@ -201,6 +216,32 @@ describe('Briefwechsel page – swap button', () => {
 	});
 });
 
+// ─── Distribution bar (bilateral only) ────────────────────────────────────────
+
+describe('Briefwechsel page – distribution bar', () => {
+	it('renders the DistributionBar when both persons are set and there are documents', async () => {
+		const data = {
+			...withPersons,
+			documents: [
+				makeDoc({ id: 'out1', sender: hansPerson, receivers: [annaPerson] }),
+				makeDoc({ id: 'in1', sender: annaPerson, receivers: [hansPerson] }),
+				makeDoc({ id: 'in2', sender: annaPerson, receivers: [hansPerson] })
+			]
+		};
+		render(Page, { data });
+		const bar = document.querySelector('[role="img"][aria-label*="Briefverteilung"]');
+		expect(bar).not.toBeNull();
+		expect(bar!.getAttribute('aria-label')).toContain('1 von Hans Müller');
+		expect(bar!.getAttribute('aria-label')).toContain('2 von Anna Schmidt');
+	});
+
+	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"]');
+		expect(bar).toBeNull();
+	});
+});
+
 // ─── Year dividers ────────────────────────────────────────────────────────────
 
 describe('Briefwechsel page – year dividers', () => {