One header for every page type. hide_title: true in front matter suppresses it for a
page that opens with its own heading, without losing the <title> and og:title
metadata.
Details
The action links are Buttons rather than the hand-rolled pill the stylesheet used to
draw: an outlined and a contained Button under this theme is what that pill was imitating,
and it is the same pair a card in any band shows.
See also
Other shell:
mui_app_bar(),
mui_app_shell(),
mui_footer()