test: consolidate E2E tests — remove duplicates, fix timeouts, parallelize sharing

- Remove duplicate bold formatting test from notes-crud.spec.ts
- Trim formatting.spec.ts from 9 to 5 tests (remove italic, inline code,
  toolbar bold, toolbar visibility — same mechanism as bold shortcut)
- Remove hardcoded waitForTimeout(500) from search.spec.ts (Playwright
  assertions already retry with built-in timeouts)
- Restructure sharing.spec.ts: 9 serial tests → 5 parallel self-contained
  tests using collabPage fixture and API-based setup
- Add collabPage fixture to helpers/fixtures.ts for sharing tests

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

tests/e2e/search.spec.ts

@@ -13,7 +13,6 @@ test.describe('Search', () => {
 
 		// When the user searches for "Grocery"
 		await page.getByTestId('search-input').fill('Grocery');
-		await page.waitForTimeout(500);
 
 		// Then "Grocery Errands" is visible in the results
 		await expect(page.getByText('Grocery Errands')).toBeVisible();
@@ -30,7 +29,6 @@ test.describe('Search', () => {
 
 		// When the user searches for "tomato"
 		await page.getByTestId('search-input').fill('tomato');
-		await page.waitForTimeout(500);
 
 		// Then "Recipe" is visible in the results
 		await expect(page.getByText('Recipe')).toBeVisible();
@@ -39,7 +37,6 @@ test.describe('Search', () => {
 	test('Scenario: Searching for a nonexistent term yields no results', async ({ authenticatedPage: page }) => {
 		// When the user searches for a term that matches nothing
 		await page.getByTestId('search-input').fill('xyznonexistent');
-		await page.waitForTimeout(500);
 
 		// Then no notes are displayed
 		await expect(page.getByTestId('note-card')).toHaveCount(0);