feat(hive-c0re): offer this hive's readiness to the swarm

The controller reads per-hive status out of a JetStream KV bucket and
nothing was writing one, so every hive rendered `never_reported`. This is
the half that makes the read path mean anything.

A hive offers; the controller never reaches down to collect. The gateway
has gone down in a way where every recovery channel ran through the one
broken thing, so a status path that depended on the controller would go
dark exactly when it is needed to diagnose the controller's own network.

What it publishes is what the hive already says about itself —
`warnings::readiness()`, the same value `/health/ready` serves. Nothing
here stamps a time: freshness is derived by the reader from when the value
landed, so a hive cannot make itself look fresher than it is, and a hive
with a wrong clock skews only its own payload.

The key is this hive's `hiveName`, which `swarm.nix` already asserts is a
key of `swarm.hives` — so a hive that evaluates at all publishes under a
name the roster knows, rather than by convention.

Publish first, then wait: a hive that has just come up is the one whose
status someone is looking at, and sleeping first would make every restart
read stale for a full interval. The interval is one decision with the
controller's staleness threshold, not two — a ratio of 2 means one lost
publish still reads fresh and two consecutive misses read stale.

Failures go to the dashboard banner through SweepHealth, debounced, at
`warn` and deliberately not `crit`: `crit` is what makes this hive report
itself degraded, and a hive that cannot reach the queue is not unhealthy —
the swarm's view of it is. Publishing `degraded` because the publish
failed would be both false and self-erasing on the next tick.

hive-c0re/Cargo.toml

@@ -9,6 +9,9 @@ workspace = true
 
 [dependencies]
 anyhow.workspace = true
+# Named directly only for the client type the swarm status publisher passes
+# around; the connect itself lives in `swarm-queue-client` below.
+async-nats.workspace = true
 axum.workspace = true
 chrono.workspace = true
 base64.workspace = true
@@ -52,6 +55,10 @@ sha2.workspace = true
 rusqlite.workspace = true
 serde.workspace = true
 serde_json.workspace = true
+# Offering this hive's status to the swarm (`swarm_status`). The same crate
+# the swarm controller reads it with, and `kv` for the same reason: the
+# bucket's name and creation config belong to neither end of it alone.
+swarm-queue-client = { workspace = true, features = ["kv"] }
 tokio.workspace = true
 tokio-stream.workspace = true
 tracing.workspace = true