hive-agent: re-send the turn-state header once a minute

The header on `$SWARM.agent-state.<agent>` went out only when a bus event
changed it, and the core subject keeps nothing for a late subscriber. An
idle agent therefore said nothing to a reader that attached after its
last change: swarm-controller after a restart showed `effective: null`
for that agent until its next turn, which can be hours.

The publish loop now also wakes every 60 s and re-sends the current
header through the same `publish` path (clearing the dedup state first).
Transitions still go out as they happen. Same subject, same grant.

An agent whose queue connection is down now logs `swarm agent state:
publish skipped` once a minute even while idle, so the
`hh-swarm-agent-state-publish-skipped` alert also fires for idle
disconnected agents, not only busy ones.

Refs #5034

swarm-controller/src/inference.rs

@@ -8,8 +8,9 @@
 //!
 //! What the agent runs on comes from its turn-state header
 //! (`$SWARM.agent-state.<agent>`), which [`Reported`] keeps the latest of.
-//! Agents publish a header only when it changes and the queue keeps none, so
-//! an agent that has not changed since this daemon started has no entry.
+//! Agents publish a header when it changes and re-send it once a minute, and
+//! the queue keeps none, so an agent has no entry for up to a minute after
+//! this daemon starts.
 
 use std::collections::{BTreeSet, HashMap};
 use std::sync::{Arc, Mutex, PoisonError};