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

hive-agent/Cargo.toml

@@ -52,8 +52,11 @@ tokio-stream.workspace = true
 tower-http.workspace = true
 tracing.workspace = true
 
+# `test-util` for `#[tokio::test(start_paused = true)]`: `swarm_agent_state`'s
+# refresh test waits out its one-minute interval on paused time.
 [dev-dependencies]
 tempfile = "3"
+tokio = { workspace = true, features = ["test-util"] }
 
 # Single harness serve-loop binary: `hive-agent` (from `src/main.rs`).
 # The sibling MCP server is its own bin crate now (`hive-agent-mcp`).