"embedded" — card-only embedded form; the HOST button drives
submission through confirm() (the historical shape, and the default).
"smartform" — the multi-method smartForm in list mode. The FORM
owns method selection and its own pay buttons; confirm() awaits the
outcome instead of submitting (call it right after mount and hide any
host pay button).
"smartform-expanded" — smartForm in list mode with the card form
pre-expanded (kr-card-form-expanded); same ownership as "smartform".
A smartForm whose token/shop resolves to cards only renders the plain card
fields, so "smartform" is safe to use for card-only sessions too.
Which krypton form mount() renders: