An agent's harness connects to the swarm queue with the agent's own
credential or not at all. The first connect retries after 5s, doubling
(7 attempts, about five minutes), with a warning per failed attempt;
when every attempt fails the harness logs an error and exits 1. Missing
coordinates (HIVE_AGENT_NATS_URL, or the secret store's BAO_ADDR /
HIVE_AGENT_NAME / certificate) fail the boot outright.
Previously the first connect's outcome was memoized for the life of the
process: a store 403 or queue refusal at boot left the agent on the
hive's shared client, or disconnected, until someone restarted it, and
an agent with no queue coordinates ran on without one. Both paths are
gone, with the hive-scoped subjects that only the shared client used.
The harness unit now restarts after 30s instead of 2s, so a swarm-wide
outage doesn't restart every agent every 2s, and has no start limit, so
it keeps coming back however long the outage lasts.
The hive's shared client credential is still imported into the harness
unit for swarm-logs; the two HIVE_AGENT_OIDC_*_FILE variables that
pointed the harness at it are dropped, as is the unset
HIVE_AGENT_OIDC_CA_FILE override.
With the fallback gone, the pieces #4944 added only for it go too:
swarm_input's skip-on-shared-client branch and swarm-queue-client's
connect_with_inbox_prefix. swarm-nats-auth's grant for the hive's shared
agent client is unchanged.
Closes#4909
235bc481b3