Invitation_cancel

Iterates rows independently. Each row goes through the same per-row checks the single-create endpoint runs (email validation, policy, role, team existence, throttle); per-row outcomes ride back in `BulkCreateInvitationResponse.results` so the admin sees partial success without scraping the audit log. Anti-enumeration doesn't constrain this surface — the endpoint requires admin auth on the calling org, so per-row outcomes don't leak across tenants.