Probe 'prepare' provisions the consumer identity via OpcUaApplicationIdentity.EnsureApplicationCertificateAsync
and exports the public DER; runner installs it in the server trusted store before start. Adds Sign
(OPCUA_MATRIX_SERVER_SECURITY=sign), untrusted-client / untrusted-server fail-closed controls per secure
mode, and OPCUA_MATRIX_ACL=off. Autoaccept stays false everywhere.
Joseph Doherty