Opaque resolved configuration returned by SSL.prepare_upgrade/1.

The immutable snapshot retains loaded trust, client credentials, wire profile, reference identity, SNI and supported upgrade options. It contains no socket, connection process, deadline, traffic secrets or ephemeral key material.

A snapshot may be reused deliberately with SSL.connect_prepared/3; each connection still generates fresh handshake material. Preparation does not establish a connection or prove resource adoption, cancellation or cleanup. Callers must not construct, modify or inspect the internal representation.