fix: use original cluster name for solo instances instead of 'solo/<node>'

- Solo instances (started with --node) now use the original cluster name for sm121.cluster label
- Added sm121.solo-node=<node_name> label to identify solo instances
- This ensures solo instances show up in the per-cluster health check

src/docker/mod.rs

@@ -72,7 +72,7 @@ pub async fn serve(
             .find_map(|c| {
                 c.nodes.iter().find(|n| n.name == nn).map(|node| {
                     let solo = Cluster {
-                        name: format!("solo/{}", node.name),
+                        name: c.name.clone(),
                         master_ib_ip: node.ib_ip.clone(),
                         nodes: vec![node.clone()],
                         extra_entities: vec![],
@@ -446,6 +446,10 @@ fn build_docker_command(ctx: &DockerCommandCtx, node: &Node, is_head: bool) -> V
     cmd.push(format!("--label sm121.recipe={}", ctx.recipe_name));
     cmd.push(format!("--label sm121.rank={}", node.rank));
     cmd.push(format!("--label sm121.cluster={}", ctx.cluster.name));
+    // Add solo-node label for single-node deployments
+    if ctx.cluster.nodes.len() == 1 && ctx.cluster.extra_entities.is_empty() {
+        cmd.push(format!("--label sm121.solo-node={}", node.name));
+    }
     if ctx.recipe.distributed_backend == Some(crate::config::DistributedBackend::Ray) {
         env.push((
             "RAY_ADDRESS",