agent: export swarm-queue connected gauge and skipped-publish counter, with dashboard panels

hive-agent/src/swarm_agent_state.rs

@@ -315,6 +315,7 @@ async fn publish(
     // has announced its own, which is smaller than any deployment sets.
     if let Err(e) = swarm_queue_client::ensure_connected(client) {
         tracing::warn!(error = %swarm_queue_client::chain(&e), "swarm agent state: publish skipped");
+        crate::otel_turn_metrics::record_swarm_queue_publish_skipped("agent_state");
         return;
     }
     // No degrade path, unlike `swarm_term`'s: every field here is a number,