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

swarmctl/src/inference.rs

@@ -151,8 +151,8 @@ fn render(s: &Settings) -> String {
 fn render_effective(e: Option<&Effective>) -> String {
     e.map_or_else(
         || {
-            "running: not reported since swarm-controller started; the agent reports on its \
-             next change\n"
+            "running: not reported since swarm-controller started; the agent reports within a \
+             minute\n"
                 .to_owned()
         },
         |e| {