docs(galaxy): fix stale SystemPlatform/alias/Galaxy doc comments (review follow-up)

Resolves the code-review notes on 95be607a + the AdminUI bundle: the
EnsureVariable docs (IOpcUaAddressSpaceSink, OtOpcUaNodeManager) and the Tag
entity doc no longer say 'Galaxy / SystemPlatform / alias'; the DriverHostActor
ForwardToMux comment now states the real equipment-tag value-routing gap (the
FullName→NodeId 'live values' milestone) instead of claiming Galaxy values map
straight through.

src/Server/ZB.MOM.WW.OtOpcUa.OpcUaServer/OtOpcUaNodeManager.cs

@@ -626,8 +626,8 @@ public sealed class OtOpcUaNodeManager : CustomNodeManager2
     ///     Ensure a Variable node exists at <paramref name="variableNodeId"/> parented under
     ///     <paramref name="parentFolderNodeId"/> (or root when null). Initial value=null, quality=Bad,
     ///     timestamp=epoch — <see cref="WriteValue"/> fills these in once driver data flows.
-    ///     Idempotent. Materialises Galaxy / SystemPlatform tags so they're browseable before the
-    ///     Galaxy driver issues SubscribeBulk.
+    ///     Idempotent. Materialises equipment-namespace tags so they're browseable before drivers
+    ///     issue SubscribeBulk.
     /// </summary>
     /// <param name="variableNodeId">The node identifier of the variable.</param>
     /// <param name="parentFolderNodeId">The node identifier of the parent folder; null to use the namespace root.</param>