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.OpcUaServer/Phase7Applier.cs

@@ -94,6 +94,43 @@ public sealed class Phase7Applier
         return new Phase7ApplyOutcome(removedCount, addedCount, changedCount, needsRebuild);
     }
 
+    /// <summary>
+    ///     #85 — build the UNS Area/Line/Equipment folder hierarchy in the address space from a
+    ///     composition snapshot. Called by <c>OpcUaPublishActor</c> after a rebuild so OPC UA
+    ///     clients browsing the server see proper folder structure instead of flat tag ids.
+    ///     Idempotent: each <c>EnsureFolder</c> call returns the existing folder if already
+    ///     present, so re-applies are cheap.
+    /// </summary>
+    public void MaterialiseHierarchy(Phase7CompositionResult composition)
+    {
+        ArgumentNullException.ThrowIfNull(composition);
+
+        foreach (var area in composition.UnsAreas)
+        {
+            SafeEnsureFolder(area.UnsAreaId, parentNodeId: null, displayName: area.DisplayName);
+        }
+        foreach (var line in composition.UnsLines)
+        {
+            SafeEnsureFolder(line.UnsLineId, parentNodeId: line.UnsAreaId, displayName: line.DisplayName);
+        }
+        foreach (var equipment in composition.EquipmentNodes)
+        {
+            // Equipment with no UnsLineId (legacy / dev rows) hang under the root.
+            var parent = string.IsNullOrWhiteSpace(equipment.UnsLineId) ? null : equipment.UnsLineId;
+            SafeEnsureFolder(equipment.EquipmentId, parentNodeId: parent, displayName: equipment.DisplayName);
+        }
+
+        _logger.LogInformation(
+            "Phase7Applier: hierarchy materialised (areas={Areas}, lines={Lines}, equipment={Equipment})",
+            composition.UnsAreas.Count, composition.UnsLines.Count, composition.EquipmentNodes.Count);
+    }
+
+    private void SafeEnsureFolder(string nodeId, string? parentNodeId, string displayName)
+    {
+        try { _sink.EnsureFolder(nodeId, parentNodeId, displayName); }
+        catch (Exception ex) { _logger.LogWarning(ex, "Phase7Applier: EnsureFolder threw for {Node}", nodeId); }
+    }
+
     private void SafeWriteAlarmState(string nodeId, bool active, bool acknowledged, DateTime ts)
     {
         try { _sink.WriteAlarmState(nodeId, active, acknowledged, ts); }