fix(journey): person chips rendered blank — share one PersonView→PersonOption projection

JourneyEditor fed GeschichteView.PersonView (no displayName) straight into
the displayName-rendering PersonMultiSelect, so every chip on a journey was
empty. The name mapping both editors need now lives once in
$lib/person/personOption.ts (with the [Unbekannt] fallback matching
GeschichteService.toView), and PersonMultiSelect/GeschichteSidebar import
the narrow PersonOption contract from there.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

frontend/src/lib/geschichte/JourneyEditor.svelte.spec.ts

@@ -394,3 +394,18 @@ describe('JourneyEditor — duplicate document aria-disabled', () => {
 		expect(option.getAttribute('aria-disabled')).toBe('true');
 	});
 });
+
+describe('JourneyEditor — person chips from GeschichteView', () => {
+	it('renders person names in the sidebar chips (PersonView carries no displayName)', async () => {
+		render(
+			JourneyEditor,
+			defaultProps({
+				geschichte: makeGeschichte({
+					persons: [{ id: 'p1', firstName: 'Anna', lastName: 'Schmidt' }]
+				})
+			})
+		);
+
+		await expect.element(page.getByText('Anna Schmidt')).toBeInTheDocument();
+	});
+});