test(playwright): add playwright report to track changes + correct playwright parameters

ci: fix actions/checkout@v6 → @v4 (v6 does not exist)

GitHub started rejecting invalid action versions at parse time,
causing every CI run to fail with 0s / 'workflow file issue'
before any jobs could start.

 * test(e2e): only no retry
 * test(e2e): use static name in tests to facilitate screenshot comparaison
 * test(e2e): update linux screenshots
 * test(e2e): adapt test due to user-vignette generation

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

tests/e2e/scenarios/helpers.ts

@@ -7,7 +7,17 @@ export const TEST_ADMIN = {
 };
 
 /**
- * Log in as the test admin and wait until the main app is ready.
+ * Log in as the test admin and wait until the main app is fully initialized.
+ *
+ * We wait for two things after the login redirect:
+ *  1. `#sidebar` — confirms the main HTML has loaded.
+ *  2. `#user-avatar-btn .user-vignette` — confirms that `setupUserMenu()` has
+ *     run and mounted the avatar vignette.  This is the earliest reliable
+ *     signal that the click-handler on the avatar button is attached, so any
+ *     subsequent test that opens the user menu will not race against JS startup.
+ *
+ * Without (2), CI (Ubuntu + Xvfb) occasionally clicks the button before the
+ * event listener is registered because the JS runtime is slower than on macOS.
  */
 export async function loginAsAdmin(page: Page) {
   await goToLoginPage(page);
@@ -15,6 +25,8 @@ export async function loginAsAdmin(page: Page) {
   await page.locator('#login-password').fill(TEST_ADMIN.password);
   await page.locator('#login-panel button[type="submit"]').click();
   await expect(page.locator('#sidebar')).toBeVisible({ timeout: 15_000 });
+  // Wait for the JS app to initialise: avatar vignette present ⟹ click handler attached.
+  await expect(page.locator('#user-avatar-btn .user-vignette')).toBeAttached({ timeout: 10_000 });
 }
 
 /**