fix(geschichten): correct three bugs found in PR review

- Pass validated documentId (not raw) to /api/geschichten — Spring backend
  declares @RequestParam UUID documentId; invalid strings cause HTTP 400
- rebuildUrl no longer deletes documentId unconditionally; clearAll and
  removeDocument handle their own documentId deletion explicitly, so
  removePerson/addPerson now preserve an active document filter
- Use ?? instead of || when falling back from doc.title to originalFilename,
  preserving an intentionally-empty title rather than overwriting it

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

frontend/src/routes/geschichten/+page.server.ts

@@ -20,7 +20,7 @@ export const load: PageServerLoad = async ({ url, fetch }) => {
 				query: {
 					status: 'PUBLISHED',
 					personId: personIds.length ? personIds : undefined,
-					documentId: rawDocumentId ?? undefined
+					documentId: documentId ?? undefined
 				}
 			}
 		}),
@@ -44,7 +44,7 @@ export const load: PageServerLoad = async ({ url, fetch }) => {
 			const doc = docResult.data;
 			documentFilter = {
 				id: documentId,
-				title: doc.title || doc.originalFilename || null
+				title: doc.title ?? doc.originalFilename ?? null
 			};
 		} else {
 			documentFilter = { id: documentId, title: null };

frontend/src/routes/geschichten/+page.svelte

@@ -28,13 +28,15 @@ const emptyMessage = $derived.by(() => {
 function rebuildUrl(personIds: string[]) {
 	const url = new URL(window.location.href);
 	url.searchParams.delete('personId');
-	url.searchParams.delete('documentId');
 	for (const id of personIds) url.searchParams.append('personId', id);
 	return url.pathname + url.search;
 }
 
 function clearAll() {
-	goto(rebuildUrl([]), { replaceState: true });
+	const url = new URL(window.location.href);
+	url.searchParams.delete('personId');
+	url.searchParams.delete('documentId');
+	goto(url.pathname + url.search, { replaceState: true });
 }
 
 function addPerson(personId: string) {
@@ -51,7 +53,9 @@ function removePerson(personId: string) {
 }
 
 function removeDocument() {
-	goto(rebuildUrl(selectedPersonIds));
+	const url = new URL(window.location.href);
+	url.searchParams.delete('documentId');
+	goto(url.pathname + url.search);
 }
 </script>
 

frontend/src/routes/geschichten/page.server.test.ts

@@ -81,6 +81,14 @@ describe('geschichten page load — documentFilter title resolution', () => {
 		expect(result.documentFilter).toEqual({ id: VALID_UUID, title: 'scan_001.jpg' });
 	});
 
+	it('preserves an empty-string title rather than falling back to filename', async () => {
+		mockApi({ docData: { id: VALID_UUID, title: '', originalFilename: 'scan_001.jpg' } });
+
+		const result = await callLoad(makeUrl({ documentId: VALID_UUID }));
+
+		expect(result.documentFilter).toEqual({ id: VALID_UUID, title: '' });
+	});
+
 	it('degrades to {id, title: null} on 404 without throwing (resolves, never rejects)', async () => {
 		// Explicit .resolves locks the no-throw guarantee — if error() were called, this would reject
 		mockApi({ docOk: false });
@@ -159,13 +167,13 @@ describe('geschichten page load — documentFilter title resolution', () => {
 		);
 	});
 
-	it('passes invalid documentId to the list API without stripping (option B)', async () => {
+	it('omits documentId from the list API when the value is not a valid UUID', async () => {
 		const mockGet = mockApi();
 
 		await callLoad(makeUrl({ documentId: 'not-a-uuid' }));
 
 		const listCall = mockGet.mock.calls.find((c) => c[0] === '/api/geschichten');
-		expect(listCall?.[1]?.params?.query?.documentId).toBe('not-a-uuid');
+		expect(listCall?.[1]?.params?.query?.documentId).toBeUndefined();
 	});
 
 	it('keeps forwarding personId filters alongside documentId', async () => {

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

@@ -206,6 +206,64 @@ describe('geschichten page — multi-person filter chips', () => {
 		});
 	});
 
+	it('removing a person chip preserves an active document filter in the URL', async () => {
+		const { goto } = await import('$app/navigation');
+		vi.mocked(goto).mockClear();
+
+		window.history.replaceState(
+			{},
+			'',
+			'/geschichten?personId=a&documentId=aaaaaaaa-bbbb-cccc-dddd-eeeeeeeeeeee'
+		);
+
+		render(Page, {
+			data: makeData({
+				personFilters: [person('a', 'Anna A')] as PageData['personFilters'],
+				documentFilter: makeDocumentFilter() as PageData['documentFilter']
+			})
+		});
+
+		const chipBtn = (await page
+			.getByRole('button', { name: /Anna A aus Filter entfernen/ })
+			.element()) as HTMLElement;
+		chipBtn.click();
+
+		await vi.waitFor(() => expect(goto).toHaveBeenCalledOnce());
+		const url = vi.mocked(goto).mock.calls[0][0] as string;
+		expect(url).not.toContain('personId=a');
+		expect(url).toContain('documentId=aaaaaaaa-bbbb-cccc-dddd-eeeeeeeeeeee');
+
+		window.history.replaceState({}, '', '/');
+	});
+
+	it('clearAll removes both person and document filters from the URL', async () => {
+		const { goto } = await import('$app/navigation');
+		vi.mocked(goto).mockClear();
+
+		window.history.replaceState(
+			{},
+			'',
+			'/geschichten?personId=a&documentId=aaaaaaaa-bbbb-cccc-dddd-eeeeeeeeeeee'
+		);
+
+		render(Page, {
+			data: makeData({
+				personFilters: [person('a', 'Anna A')] as PageData['personFilters'],
+				documentFilter: makeDocumentFilter() as PageData['documentFilter']
+			})
+		});
+
+		const allBtn = (await page.getByRole('button', { name: 'Alle' }).element()) as HTMLElement;
+		allBtn.click();
+
+		await vi.waitFor(() => expect(goto).toHaveBeenCalledOnce());
+		const url = vi.mocked(goto).mock.calls[0][0] as string;
+		expect(url).not.toContain('personId');
+		expect(url).not.toContain('documentId');
+
+		window.history.replaceState({}, '', '/');
+	});
+
 	describe('empty state precedence', () => {
 		it('shows geschichten_empty_for_document when only document filter is active', async () => {
 			render(Page, {