test(transcription): harden annotation-delete specs and e2e (#722)

- Fix a stale test title that still claimed a delete button is visible.
- Strengthen the two "never renders a delete button" contract tests
  (AnnotationShape + AnnotationLayer specs) to assert the annotation
  element has zero descendant <button> elements, not just the absence of
  the removed testid (a near-tautology now that the testid is gone).
- Harden the e2e delete test: guard countBefore > 0 so a missing seed
  fails clearly instead of asserting toHaveCount(-1), and capture the
  deleted annotation's testid to assert that specific element is gone
  (identity check) alongside the count drop.

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

frontend/e2e/documents.spec.ts

@@ -382,6 +382,9 @@ test.describe('PDF annotations — admin', () => {
 		});
 		// Record count now — the draw test may have created more than one annotation
 		const countBefore = await page.locator('[data-testid^="annotation-"]').count();
+		// Guard against a missing seed: without this, a count of 0 would turn the
+		// post-delete assertion into toHaveCount(-1) and fail with a misleading timeout.
+		expect(countBefore).toBeGreaterThan(0);
 
 		// Enable annotate mode — deletion is only available while annotating
 		await page.getByRole('button', { name: /^annotieren$/i }).click();
@@ -389,6 +392,10 @@ test.describe('PDF annotations — admin', () => {
 		// The on-canvas delete button was removed (issue #722). Delete via the
 		// kept keyboard shortcut: focus an annotation, press Delete, confirm.
 		const annotation = page.locator('[data-testid^="annotation-"]').first();
+		// Capture the identity of the specific annotation we delete so we can assert
+		// that exact element is gone afterwards — a count drop alone is identity-blind.
+		const deletedTestId = await annotation.getAttribute('data-testid');
+		expect(deletedTestId).toBeTruthy();
 		await annotation.click();
 		await annotation.press('Delete');
 
@@ -397,6 +404,10 @@ test.describe('PDF annotations — admin', () => {
 		await expect(page.locator('[data-testid^="annotation-"]')).toHaveCount(countBefore - 1, {
 			timeout: 8000
 		});
+		// Identity check: the specific annotation we deleted must no longer exist.
+		await expect(page.locator(`[data-testid="${deletedTestId}"]`)).toHaveCount(0, {
+			timeout: 8000
+		});
 
 		await page.screenshot({ path: 'test-results/e2e/annotation-deleted.png' });
 	});