docs(uns): clarify HasLazyChildren + cluster EntityId, add tie-break test (review I1/I2/M2)

src/Server/ZB.MOM.WW.OtOpcUa.AdminUI/Uns/UnsNode.cs

@@ -40,7 +40,12 @@ public sealed class UnsNode
     /// <summary>Badge count. For equipment this is tag + virtual-tag count; for container nodes it is the direct child count.</summary>
     public int ChildCount { get; set; }
 
-    /// <summary>True when this node has children that are loaded lazily (equipment with <see cref="ChildCount"/> &gt; 0).</summary>
+    /// <summary>
+    /// Gets a value indicating whether this node has children that load lazily (equipment with tags/virtual tags).
+    /// Structural nodes (Cluster/Area/Line) always carry <c>false</c> even when they have eager children, so a
+    /// renderer must decide whether to show an expand chevron with <c>Children.Count &gt; 0 || HasLazyChildren</c>,
+    /// not on <c>HasLazyChildren</c> alone.
+    /// </summary>
     public bool HasLazyChildren { get; init; }
 
     /// <summary>Eagerly-materialised children. Empty for lazy-loaded equipment until expanded.</summary>
@@ -162,7 +167,7 @@ public static class UnsTreeAssembly
                 ? cluster.Name
                 : $"{cluster.Site} ({cluster.Name})",
             ClusterId = cluster.ClusterId,
-            EntityId = cluster.ClusterId,
+            EntityId = cluster.ClusterId, // Cluster's own logical id IS its ClusterId — EntityId mirrors it for uniform navigation.
             HasLazyChildren = false,
         };
         node.Children.AddRange(areaNodes);