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.Configuration/Entities/Tag.cs

@@ -31,8 +31,7 @@ public sealed class Tag
     public string? DeviceId { get; set; }
 
     /// <summary>
-    ///     Set when the tag belongs to an Equipment (driver tag OR Galaxy alias); NULL for
-    ///     SystemPlatform mirror tags.
+    ///     Set when the tag belongs to an Equipment; NULL for FolderPath-scoped (namespace-root) tags.
     /// </summary>
     public string? EquipmentId { get; set; }
 
@@ -41,7 +40,7 @@ public sealed class Tag
     /// </summary>
     public required string Name { get; set; }
 
-    /// <summary>Only used when <see cref="EquipmentId"/> is NULL (SystemPlatform namespace).</summary>
+    /// <summary>Only used when <see cref="EquipmentId"/> is NULL (FolderPath-scoped namespace tag).</summary>
     public string? FolderPath { get; set; }
 
     /// <summary>OPC UA built-in type name (Boolean / Int32 / Float / etc.).</summary>