'**.example.com' covers the apex and subdomains at any depth;
'*.example.com' covers exactly one subdomain level (neither apex nor
deeper) — analogous to permission scope wildcards, and sidestepping the
DNS/TLS/nginx ambiguity around '*.'. This also allows excluding the apex
where wanted. The seeded/default entry becomes '**.{rp-id}' (init,
add-domain, legacy empty-origins conversion, branch-era '*' sanitize
rewrite).