The bus account has JetStream, and the control plane's client has its own inbox

Two refusals the first live connections met. A user in the MESH account was told
"JetStream not enabled for account" the first time it bound a consumer: with
accounts defined, JetStream is enabled per account, not only globally — the
account's setting, which the mesh owns, not the server's block, which it does not.
And the control plane's client used a random inbox prefix where it is granted
exactly _INBOX.<its user>.>, so the server's first answer could not reach it. The
prefix now follows from the user in the URL, for every principal that dials so.

internal/broker/jetstream.go

@@ -42,6 +42,12 @@ func Dial(url string, opts ...nats.Option) (*JetStream, error) {
 		}
 		opts = append(opts, nats.Secure(pinned))
 	}
+	// **Its own inbox, and nothing wider.** Every principal is granted `_INBOX.<its user>.>` and
+	// no other inbox; the client's default prefix is random, and the server refused the first
+	// subscription to it (2026-09-28). The user is in the URL, so the prefix follows from it.
+	if user, _, _ := CredentialIn(url); user != "" {
+		opts = append(opts, nats.CustomInboxPrefix("_INBOX."+user))
+	}
 	// The address in an error is the address alone. The URL carries this controller's password,
 	// and an error here is written on the assumption it will be logged.
 	where := BareAddress(url)