Type Alias
routine is anything the learner can do again — confirming an address,
choosing a new password — and wears the gold primary. destructive is a
link that cannot be taken back, and wears the destructive treatment so it
never looks like a reward. The template declares this, not the caller: the
fact that deletion is irreversible belongs to the delete template.
What the email's one link does, which decides how its button is painted.