docs(galaxy): neutralize remaining stale SystemPlatform/alias terminology in comments + a test name

Replace "SystemPlatform mirror tag", "Galaxy alias", and "SystemPlatform-kind" in doc-comments and
test names with neutral accurate wording ("FolderPath-scoped tag", "EquipmentId == null", etc.).
No code, logic, or test bodies changed — comments and one test method name only.

src/Core/ZB.MOM.WW.OtOpcUa.Core/OpcUa/EquipmentNodeWalker.cs

@@ -9,7 +9,7 @@ namespace ZB.MOM.WW.OtOpcUa.Core.OpcUa;
 ///     <see cref="Configuration.Entities.Namespace"/> from the Config DB's
 ///     <c>UnsArea</c> / <c>UnsLine</c> / <c>Equipment</c> / <c>Tag</c> rows. Runs during
 ///     address-space build per <see cref="IDriver"/> whose
-///     <c>Namespace.Kind = Equipment</c>; SystemPlatform-kind namespaces (Galaxy) are
+///     <c>Namespace.Kind = Equipment</c>; non-Equipment namespaces are
 ///     exempt per decision #120 and reach this walker only indirectly through
 ///     <see cref="ITagDiscovery.DiscoverAsync"/>.
 /// </summary>
@@ -21,7 +21,7 @@ namespace ZB.MOM.WW.OtOpcUa.Core.OpcUa;
 ///         folder node at the UNS level-5 segment; every <see cref="Tag"/> bound to an
 ///         Equipment (non-null <see cref="Tag.EquipmentId"/>) becomes a variable node under
 ///         it. Driver-discovered tags that have no Config-DB row are not added by this
-///         walker — the ITagDiscovery path continues to exist for the SystemPlatform case +
+///         walker — the ITagDiscovery path continues to exist for FolderPath-scoped tags +
 ///         for enrichment, but Equipment-kind composition is fully Tag-row-driven.
 ///     </para>
 ///