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_newsletter.py

@@ -26,6 +26,9 @@ def test_subscribe_valid_email_shows_confirmation(page: Page, base_url: str) ->
 def test_subscribe_invalid_email_shows_error(page: Page, base_url: str) -> None:
     page.goto(f"{base_url}/", wait_until="networkidle")
     form = _nav_newsletter_form(page)
+    # Disable the browser's native HTML5 email validation so the JS handler
+    # fires and sends the bad value to the server (which returns 400).
+    page.evaluate("document.querySelector('nav form[data-newsletter-form]').setAttribute('novalidate', '')")
     form.locator('input[type="email"]').fill("not-an-email")
     form.get_by_role("button", name="Subscribe").click()