test(timeline): assert submit-disabled transition and ≥44px chip targets

Tighten the review-flagged test gaps (no production change):
- submitting state: the old test only asserted the button was initially
  enabled (a tautology). Now stub a never-resolving fetch, click Speichern, and
  assert the button gains `disabled` — exercising the double-submit guard
  (Decision 8).
- the two redirect-throwing save tests now use `await expect(...).rejects` so a
  future missing redirect fails loudly instead of being swallowed by try/catch.
- the YEAR end-date-hide assertion uses getByLabelText('Enddatum') not-present,
  symmetric with the RANGE reveal, instead of a raw #eventDateEnd querySelector.
- PersonMultiSelect + DocumentMultiSelect: assert the chip remove button carries
  the min-h-[44px]/min-w-[44px] target the rtm cites for REQ-017.

Addresses PR #832 review (Tester + Requirements Engineer test-coverage concerns).

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

frontend/src/lib/document/DocumentMultiSelect.svelte.spec.ts

@@ -157,4 +157,14 @@ describe('DocumentMultiSelect — remove', () => {
 			document.querySelector<HTMLInputElement>('input[type="hidden"][name="documentIds"]')
 		).toBeNull();
 	});
+
+	// REQ-017 (#781): chip remove targets must be ≥44px for the 60+ audience.
+	it('renders a ≥44px touch target on the chip remove button', async () => {
+		render(DocumentMultiSelect, {
+			selectedDocuments: [docFactory('d1', 'Brief A')]
+		});
+		const removeBtn = (await page.getByLabelText('Entfernen').element()) as HTMLElement;
+		expect(removeBtn.className).toContain('min-h-[44px]');
+		expect(removeBtn.className).toContain('min-w-[44px]');
+	});
 });