{{! Sticky header is hidden from screen readers because it contains duplicated content that is already accessible to assistive tech via landmark roles, element type, and other navigation methods. The interactive elements in the sticky header should have the `tabindex="-1"` attribute set to ensure the header is also not tab accessible. See https://dequeuniversity.com/rules/axe/4.1/aria-hidden-focus and https://phabricator.wikimedia.org/T290201 for more context. The exception to this is the TOC in the sticky header, which is not duplicated and is moved into the sticky header in the DOM. We apply `aria-hidden` to all the contents of the sticky header except for the TOC. }}