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 GitBook renews the certificate before expiry without user action, or whether the domain must be removed and re-added to trigger re-issuance. Let's Encrypt certificates expire after 90 days, so the renewal policy matters for any production docs site.

Assume a current GitBook cloud workspace (not the legacy self-hosted version) with a custom domain already showing "Active". Verification would involve checking the certificate's expiry date in browser dev tools and watching whether it rotates without intervention, but waiting months is impractical for planning.

Does GitBook automatically renew custom-domain certificates before expiration? If renewal fails (e.g., DNS changed or rate limits hit), what status does the domain badge show, and is there any notification? Is re-adding the domain the documented recovery path?