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/Core/ZB.MOM.WW.OtOpcUa.Configuration/Entities/Tag.cs

@@ -4,10 +4,9 @@ namespace ZB.MOM.WW.OtOpcUa.Configuration.Entities;
 
 /// <summary>
 ///     One canonical tag (signal) in a cluster's generation. <see cref="EquipmentId"/> set ⟺ the
-///     tag participates in the Equipment tree, regardless of the driver's namespace kind. A
-///     <c>GalaxyMxGateway</c>-bound equipment tag is an <em>alias</em> — a Galaxy attribute surfaced
-///     under a UNS name, with its Galaxy reference carried in <c>TagConfig.FullName</c>.
-///     <see cref="EquipmentId"/> is NULL for SystemPlatform mirror tags (FolderPath-scoped).
+///     tag participates in the Equipment tree. A <c>GalaxyMxGateway</c>-bound equipment tag is an
+///     ordinary equipment tag (GalaxyMxGateway is a standard Equipment-kind driver) that carries its
+///     Galaxy attribute reference in <c>TagConfig.FullName</c> — there is no separate alias concept.
 /// </summary>
 public sealed class Tag
 {