feat(opcua): #85 UNS Area/Line/Equipment folder hierarchy in SDK

Phase7Composer now carries UnsAreaProjection + UnsLineProjection lists so
the applier can materialise the full UNS topology in the OPC UA address
space. New IOpcUaAddressSpaceSink.EnsureFolder(folderNodeId, parentNodeId,
displayName) seam (no-op default, recorded in tests, forwarded by
DeferredAddressSpaceSink, implemented by SdkAddressSpaceSink). The SDK-
side OtOpcUaNodeManager gains an EnsureFolder API that creates
FolderState nodes with proper parent linkage; RebuildAddressSpace now
clears folders too so re-applies don't accumulate stale topology.

Phase7Applier.MaterialiseHierarchy walks composition.UnsAreas →
composition.UnsLines → composition.EquipmentNodes, calling EnsureFolder
with the correct parent at each level. Idempotent — calling twice with
the same composition is a no-op. OpcUaPublishActor.HandleRebuild invokes
it after Phase7Applier.Apply so OPC UA clients browsing the server now
see Area/Line/Equipment as proper folders rather than flat tag ids.

DeploymentArtifact.ParseComposition reads UnsAreas + UnsLines from the
JSON snapshot the ControlPlane emits, populating the new fields when
present.

Phase7Composer.Compose now accepts UnsAreas + UnsLines; a 3-arg overload
preserves the old signature for legacy callers + existing tests. The
Phase7CompositionResult convenience ctor likewise keeps the planner
tests working without UNS data.

3 new hierarchy tests (pure unit + boot-verify against a real
OtOpcUaSdkServer); OpcUaServer suite is 48/48 green (was 45, +3),
Runtime 74/74 unchanged.

Closes #85.

src/Server/ZB.MOM.WW.OtOpcUa.Runtime/Drivers/DeploymentArtifact.cs

@@ -89,34 +89,34 @@ public static class DeploymentArtifact
     /// </summary>
     public static Phase7CompositionResult ParseComposition(ReadOnlySpan<byte> blob)
     {
-        if (blob.IsEmpty)
-        {
-            return new Phase7CompositionResult(
-                Array.Empty<EquipmentNode>(),
-                Array.Empty<DriverInstancePlan>(),
-                Array.Empty<ScriptedAlarmPlan>());
-        }
+        if (blob.IsEmpty) return Empty();
 
         try
         {
             using var doc = JsonDocument.Parse(blob.ToArray());
             var root = doc.RootElement;
 
+            var areas = ReadArray(root, "UnsAreas", ReadAreaProjection);
+            var lines = ReadArray(root, "UnsLines", ReadLineProjection);
             var equipment = ReadArray(root, "Equipment", ReadEquipmentNode);
             var drivers = ReadArray(root, "DriverInstances", ReadDriverPlan);
             var alarms = ReadArray(root, "ScriptedAlarms", ReadAlarmPlan);
 
-            return new Phase7CompositionResult(equipment, drivers, alarms);
+            return new Phase7CompositionResult(areas, lines, equipment, drivers, alarms);
         }
         catch (JsonException)
         {
-            return new Phase7CompositionResult(
-                Array.Empty<EquipmentNode>(),
-                Array.Empty<DriverInstancePlan>(),
-                Array.Empty<ScriptedAlarmPlan>());
+            return Empty();
         }
     }
 
+    private static Phase7CompositionResult Empty() => new(
+        Array.Empty<UnsAreaProjection>(),
+        Array.Empty<UnsLineProjection>(),
+        Array.Empty<EquipmentNode>(),
+        Array.Empty<DriverInstancePlan>(),
+        Array.Empty<ScriptedAlarmPlan>());
+
     private static IReadOnlyList<T> ReadArray<T>(JsonElement root, string propertyName, Func<JsonElement, T?> reader)
         where T : class
     {
@@ -137,12 +137,31 @@ public static class DeploymentArtifact
 
     private static string IdentityOf<T>(T item) where T : class => item switch
     {
+        UnsAreaProjection a => a.UnsAreaId,
+        UnsLineProjection l => l.UnsLineId,
         EquipmentNode e => e.EquipmentId,
         DriverInstancePlan d => d.DriverInstanceId,
         ScriptedAlarmPlan a => a.ScriptedAlarmId,
         _ => string.Empty,
     };
 
+    private static UnsAreaProjection? ReadAreaProjection(JsonElement el)
+    {
+        var id = el.TryGetProperty("UnsAreaId", out var idEl) ? idEl.GetString() : null;
+        var name = el.TryGetProperty("Name", out var nameEl) ? nameEl.GetString() : null;
+        if (string.IsNullOrWhiteSpace(id)) return null;
+        return new UnsAreaProjection(id!, name ?? id!);
+    }
+
+    private static UnsLineProjection? ReadLineProjection(JsonElement el)
+    {
+        var id = el.TryGetProperty("UnsLineId", out var idEl) ? idEl.GetString() : null;
+        var areaId = el.TryGetProperty("UnsAreaId", out var areaEl) ? areaEl.GetString() : null;
+        var name = el.TryGetProperty("Name", out var nameEl) ? nameEl.GetString() : null;
+        if (string.IsNullOrWhiteSpace(id) || string.IsNullOrWhiteSpace(areaId)) return null;
+        return new UnsLineProjection(id!, areaId!, name ?? id!);
+    }
+
     private static EquipmentNode? ReadEquipmentNode(JsonElement el)
     {
         var id = el.TryGetProperty("EquipmentId", out var idEl) ? idEl.GetString() : null;

src/Server/ZB.MOM.WW.OtOpcUa.Runtime/OpcUa/OpcUaPublishActor.cs

@@ -185,6 +185,12 @@ public sealed class OpcUaPublishActor : ReceiveActor
 
             var outcome = _applier.Apply(plan);
             _lastApplied = composition;
+
+            // #85 — after the plan diff lands, rebuild the UNS folder hierarchy so OPC UA
+            // clients see Area/Line/Equipment as proper folders. Idempotent; Phase7Applier
+            // skips folders that already exist with the same node id.
+            _applier.MaterialiseHierarchy(composition);
+
             OtOpcUaTelemetry.OpcUaSinkWrite.Add(1, new KeyValuePair<string, object?>("kind", "rebuild"));
             _log.Info("OpcUaPublish: applied rebuild (correlation={Correlation}, added={Added}, removed={Removed}, changed={Changed}, rebuild={Rebuild})",
                 msg.Correlation, outcome.AddedNodes, outcome.RemovedNodes, outcome.ChangedNodes, outcome.RebuildCalled);