v3 batch1 contracts: RawPaths identity helper + reshaped greenfield entities

Shared-type foundation for Batch 1 fan-out (coordinator contracts commit):
- New Commons/Types/RawPaths.cs — the v3 identity authority (Build/Combine/
  Split/Leaf/TryParent/ValidateSegment, ordinal comparer).
- New entities RawFolder, TagGroup, UnsTagReference.
- Reshape DriverInstance (drop NamespaceId, add nullable RawFolderId),
  Tag (require DeviceId, add nullable TagGroupId, drop DriverInstanceId/
  EquipmentId/FolderPath, keep WriteIdempotent), Equipment (drop
  DriverInstanceId/DeviceId), Device (doc: now universal), ServerCluster
  (nav Namespaces -> RawFolders).
- Delete Namespace, EquipmentImportBatch(+Row), NamespaceKind enum.
- DriverTypeMetadata: drop AllowedNamespaceKinds + NamespaceKindCompatibility.

Solution is intentionally red below the foundation projects until Wave C
integrates. Commons + Core.Abstractions compile green.

src/Core/ZB.MOM.WW.OtOpcUa.Configuration/Enums/NamespaceKind.cs

@@ -1,19 +0,0 @@
-namespace ZB.MOM.WW.OtOpcUa.Configuration.Enums;
-
-/// <summary>OPC UA namespace kind. One of each kind per cluster per generation.</summary>
-public enum NamespaceKind
-{
-    /// <summary>
-    ///     Equipment namespace — raw signals from native-protocol drivers (Modbus, AB CIP, AB Legacy,
-    ///     S7, TwinCAT, FOCAS, and OpcUaClient when gatewaying raw equipment). UNS 5-level hierarchy
-    ///     applies.
-    /// </summary>
-    Equipment,
-
-    /// <summary>
-    ///     Reserved for future replay driver per handoff §"Digital Twin Touchpoints" — not populated
-    ///     in v2.0 but enum value reserved so the schema does not need to change when the replay
-    ///     driver lands.
-    /// </summary>
-    Simulated,
-}