A remote hive dialled nothing until an operator copied the queue's URL
into it, though the URL is the same string everywhere. statusPublish.natsUrl,
queue.agentNatsUrl and controller.queue.natsUrl now default to
tls://<swarm.nats.domain>:<port> unconditionally.
The statusPublish assertion treated a URL without a secret as a half
config. With the URL a default on every hive, only the secret claims
publishing: the assertion now refuses a secret without a URL or token
endpoint, and hive-c0re's status environment is gated on the secret too,
so a hive without one publishes nothing instead of reading a missing
credential.