Mail a legacy passwordless applicant a link to set their password.

Onboarding Master PRD §3.2 step 6. The applicant-facing door is the gate card's "Set my password", and it covers everybody who reaches it. This covers the ones who do not: the physician who emails support instead of clicking, or who never gets far enough to see the card because they gave up at the sign-in form.

THREE THINGS IT DELIBERATELY IS NOT:

• Not a new credential path. It mints the ordinary password reset, through the same mint_password_reset the forgot door uses, so the ceiling on live resets and the provenance row are shared rather than reimplemented.
• Not an approval. Setting a password leaves verification_status untouched; this hands somebody the ability to sit their examination, not a decision about them.
• Not available for an account that HAS a password. Refused with a 400 rather than silently mailing a reset, because an admin clicking this on the wrong row would otherwise be a way to hand out reset links for live accounts — the exact hazard _needs_credentials exists to bound.