feat(#3124): converge the hive onto the agent set the swarm declares

The deploy event is a nudge with no second path: core NATS is
at-most-once, so a hive that was down when the controller published
simply never learns that an agent is meant to exist here. This adds the
repair path — one boot-time DAG node that reads this hive's own key in
the `hive-wanted` bucket and converges the agents it names.

Two semantics settled on the issue thread, and both are places where a
plausible implementation is the wrong one:

- **Absence is not a deletion order.** No bucket, no key, or an agent
  the value does not name all mean the controller has said nothing.
  Swarm-side lifecycle does not yet cover agents that predate it, so
  "converge to exactly this set" would tear down every agent the swarm
  has not adopted. `plan` only ever inspects the agents a declaration
  names.
- **An unrecognised state is inert.** `AgentState` is an open enum: a
  value this build cannot read deserialises into `Unrecognised` and is
  left alone. A closed enum would force "not `Up`" onto a state like
  `paused`, so a controller that learned a new value would take agents
  down on every hive not yet updated.

Divergence is measured against the hive's **stored power intent**, not
the container's observed running state — an agent that is down while its
intent says `Up` is already the boot reconcile's work, and a loop reading
`is_running` would insert a start DAG behind that reconcile's back on
every boot. A hive that already agrees with its declaration queues
nothing at all.

`queue_first_deploy` is extracted from the deploy-event path rather than
open-coded here, for the power-intent seed: without it `first_deploy`'s
tail `Reconcile` seeds `Wanted` from a container that exists but has not
started yet, which locks the agent to `Offline` on its first reconcile.

The read is authorised as-is: `store.get` takes async-nats' direct-get
arm (the KV bucket is created with `allow_direct`), which is exactly the
`$JS.API.DIRECT.GET.KV_hive-wanted.$KV.hive-wanted.<hive>` subject
`swarm-nats-auth` grants a hive. The fallback subject is not granted, and
a refused NATS request surfaces as a timeout rather than an error.

Nothing writes the bucket yet — the controller-side writer is the other
half of #3124, so this does not close it.

hive-c0re/src/workers/mod.rs

@@ -1,7 +1,8 @@
 //! Background tasks and periodic sweeps: crash/login watcher, the
 //! scheduled-prompt delivery loop, boot-time auto-update
 //! reconcile, the agent-sockets.json writer loop, the MCP socket listener
-//! reconcile loop, and knowledge-repo sync. Each submodule is re-exported
+//! reconcile loop, knowledge-repo sync, and the swarm wanted-state pull.
+//! Each submodule is re-exported
 //! at the crate root, so `crate::crash_watch::…` etc. keep working unchanged.
 
 pub mod agent_sockets;
@@ -10,3 +11,4 @@ pub mod crash_watch;
 pub mod knowledge;
 pub mod mcp_sockets;
 pub mod scheduled_prompts_worker;
+pub mod wanted;