Custom domain SSL renewal: does GitBook auto-renew the Let's Encrypt certificate, or must the domain be re-added?
GitBook's custom-domain publishing flow provisions a Let's Encrypt certificate automatically once the domain's CNAME or A record resolves to GitBook's service IPs, and the UI badge moves from "Pending SSL" to "Active" after issuance. That part is documented and verifiable. What the documentation does not state clearly is the long-term lifecycle: whether GitB