The bus presents the mesh's own certificate, which names nothing a public verifier
accepts; the client verified by name and failed against a bus that was answering
("certificate is not valid for any names", 2026-09-28). It now pins the leaf's
fingerprint from MESH_BROKER_CERTIFICATE, as every host does. And a connection
error named the whole URL, password included — the address alone now.
jschoubben