test(geschichten): decouple multi-person e2e from seed names

The multi-person filter e2e previously typed 'a' then 'b' into the
typeahead and trusted the dev seed to contain matching names.
If the seed ever changes, the test would silently degrade — both
calls might resolve to the same row, or the listbox might never
populate.

Refactor to use a single broadly-occurring probe vowel ('e') and
extract person ids straight from the listbox option DOM (the option
id encodes the person id as `${listboxId}-option-${personId}`).
For the second pick, iterate options and select the first whose
id differs from the first selection. The test now only depends on
the seed having ≥2 distinct persons whose name contains 'e' — a
much weaker, more durable assumption — and asserts on the URL
params with full equality instead of toHaveLength + first-element
spot checks.

Addresses Sara's iteration-3 concern #4 on PR #382.

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

frontend/e2e/geschichten.spec.ts

@@ -68,43 +68,71 @@ test.describe('Geschichten — writer + reader journey', () => {
 		await page.goto('/geschichten');
 		await page.waitForSelector('[data-hydrated]');
 
-		// We need two persons to filter by. Open the picker and pick one whose name
-		// the dev seed reliably contains. Then open the picker again and pick a
-		// second one. Picking is via the typeahead — we type, wait for the listbox,
-		// click the first option.
-		async function pickPerson(query: string) {
+		// We need two distinct persons to filter by, but we don't want to couple this
+		// test to specific seed names. Strategy: type a single broadly-occurring vowel
+		// ("e" is present in the vast majority of German names), open the listbox,
+		// and pick whichever option matches the predicate.
+		//
+		// option DOM ids encode the person id as `${listboxId}-option-${personId}`,
+		// so we can identify the *first different* option without knowing the seed.
+		const PROBE = 'e';
+
+		async function openPicker() {
 			await page.getByRole('button', { name: /Person wählen/ }).click();
 			const input = page.getByRole('combobox', { name: /Person wählen/ });
-			await input.fill(query);
-			// Wait for at least one option in the listbox, then click it
-			const firstOption = page.getByRole('option').first();
-			await expect(firstOption).toBeVisible();
-			await firstOption.click();
+			await input.fill(PROBE);
+			// Wait for the listbox to be populated.
+			await expect(page.getByRole('option').first()).toBeVisible();
 		}
 
-		await pickPerson('a');
-		await page.waitForURL(/personId=/);
-		const firstUrl = new URL(page.url());
-		const firstIds = firstUrl.searchParams.getAll('personId');
-		expect(firstIds).toHaveLength(1);
+		async function pickFirstOption(): Promise<string> {
+			const opt = page.getByRole('option').first();
+			const optId = (await opt.getAttribute('id')) ?? '';
+			const personId = optId.split('-option-')[1] ?? '';
+			expect(personId).not.toEqual('');
+			await opt.click();
+			return personId;
+		}
 
-		await pickPerson('b');
+		async function pickFirstOptionDifferentFrom(excludeId: string): Promise<string> {
+			// Iterate through visible options and return the first whose person id != excludeId.
+			const optionCount = await page.getByRole('option').count();
+			for (let i = 0; i < optionCount; i++) {
+				const candidate = page.getByRole('option').nth(i);
+				const optId = (await candidate.getAttribute('id')) ?? '';
+				const personId = optId.split('-option-')[1] ?? '';
+				if (personId && personId !== excludeId) {
+					await candidate.click();
+					return personId;
+				}
+			}
+			throw new Error(
+				`Expected at least two distinct persons matching "${PROBE}" in the seed, found only one.`
+			);
+		}
+
+		await openPicker();
+		const firstId = await pickFirstOption();
+		await page.waitForURL(/personId=/);
+		const firstIds = new URL(page.url()).searchParams.getAll('personId');
+		expect(firstIds).toEqual([firstId]);
+
+		await openPicker();
+		const secondId = await pickFirstOptionDifferentFrom(firstId);
 		await page.waitForURL((url) => url.searchParams.getAll('personId').length === 2);
-		const secondUrl = new URL(page.url());
-		const secondIds = secondUrl.searchParams.getAll('personId');
-		expect(secondIds).toHaveLength(2);
-		expect(secondIds[0]).toBe(firstIds[0]); // first one persists
-		expect(secondIds[1]).not.toBe(firstIds[0]); // second is different
+		const secondIds = new URL(page.url()).searchParams.getAll('personId');
+		expect(secondIds).toEqual([firstId, secondId]);
+		expect(secondId).not.toEqual(firstId);
 
 		// Two chips visible — find them by their remove-aria-label pattern
 		const chipButtons = page.getByRole('button', { name: /aus Filter entfernen/ });
 		await expect(chipButtons).toHaveCount(2);
 
-		// Remove the first chip — URL drops to one param
+		// Remove the first chip — URL drops to one param, only the second id remains
 		await chipButtons.first().click();
 		await page.waitForURL((url) => url.searchParams.getAll('personId').length === 1);
 		const finalIds = new URL(page.url()).searchParams.getAll('personId');
-		expect(finalIds).toEqual([secondIds[1]]);
+		expect(finalIds).toEqual([secondId]);
 	});
 
 	test('AxeBuilder finds no critical violations on the index', async ({ page }) => {