A hive publishing its own status needs the same connect the controller
already has - mint an authelia token, present it at CONNECT for the
callout responder, let async-nats re-run the callback per attempt. Only
the use differs: the controller reads, a hive writes.
Copying it would put credential handling in two places, and a
token-refresh fix would then have to be found twice. That is the same
reasoning that already put hive-sock-client in its own crate rather than
in each daemon that speaks to a unix socket.
`from_env` takes a prefix rather than hardcoding SWARM_CONTROLLER_*: the
variables belong to the consuming unit, since a NixOS module sets them
alongside its other options. What is shared is the RULE - all four
together or none at all - not the spelling. The half-set case gains a
test, because it is the case the rule exists for and it previously had
none.
No jetstream/kv feature on the crate: it ends at a connected client, and
what a consumer does with it should be visible in that consumer's own
Cargo.toml.
Behaviour-preserving, and proven that way rather than by inspection: the
full behavioural gate (real nats-server, credential rotation, mutation)
is 20/0 unchanged, and the controller's own tests still pass.
