fix: resolve 5 E2E test failures from first CI run

- test_homepage_title_contains_brand: to_have_title() requires a string or
  regex, not a lambda; switch to re.compile('No Hype AI')
- test_granular_preferences_save_dismisses_banner: wrong element clicked to
  open <details>; use 'details summary' locator directly
- test_subscribe_invalid_email_shows_error: browser HTML5 email validation
  swallows the submit event before the JS handler fires; add 'novalidate' via
  evaluate() so the fetch still runs and the server returns 400
- test_copy_link_button_updates_text: clipboard API unavailable in headless
  Docker; add polyfill + pre-grant permissions in conftest page fixture so
  the JS success path runs and button text becomes 'Copied'
- test_comments_section_absent_when_disabled: guard against Wagtail's
  add_child() resetting BooleanField defaults by calling an explicit
  .update(comments_enabled=False) + re-setting on the instance before
  save_revision().publish(); also tighten test to assert 200 + correct title

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

e2e/test_cookie_consent.py

@@ -43,13 +43,11 @@ def test_granular_preferences_save_dismisses_banner(page: Page, base_url: str) -
     banner = page.locator("#cookie-banner")
     expect(banner).to_be_visible()
 
-    # Expand the "Manage preferences" details section
-    banner.get_by_role("group").first.click()
-    # Or use the summary text
-    page.get_by_text("Manage preferences").click()
+    # Click the <summary> element to expand <details> inside the banner
+    banner.locator("details summary").click()
 
-    # Check analytics, leave advertising unchecked
-    analytics_checkbox = page.locator('input[name="analytics"]')
+    # Analytics checkbox is now revealed; check it and save
+    analytics_checkbox = banner.locator('input[name="analytics"]')
     expect(analytics_checkbox).to_be_visible()
     analytics_checkbox.check()