feat(opcua): materialise SystemPlatform tags (Galaxy) as OPC UA variables

Closes the gap where Tag rows with EquipmentId=NULL + Namespace.Kind=SystemPlatform
(Galaxy hierarchy) existed in ConfigDb but were never surfaced in the OPC UA
address space. Now they materialise as Variable nodes under a folder named for
their FolderPath, browseable through any OPC UA client.

Layers touched:

- IOpcUaAddressSpaceSink: new EnsureVariable(nodeId, parentFolderId, displayName,
  dataType) signature on the sink interface, NullSink, DeferredSink, SdkSink.
- OtOpcUaNodeManager.EnsureVariable: creates a BaseDataVariableState parented
  under the named folder (or root), initial Value=null +
  StatusCode=BadWaitingForInitialData; resolves Tag.DataType strings to the
  matching OPC UA built-in NodeId. Idempotent.
- Phase7CompositionResult: new GalaxyTags collection of GalaxyTagPlan records
  carrying (TagId, DriverInstanceId, FolderPath, DisplayName, DataType,
  MxAccessRef). Constructor overloads keep existing call sites compiling.
- Phase7Composer.Compose: now takes Tag + Namespace inputs, filters for
  SystemPlatform-namespace tags with EquipmentId=NULL, emits GalaxyTagPlan
  rows with MXAccess ref "FolderPath.Name".
- Phase7Plan: new AddedGalaxyTags / RemovedGalaxyTags / ChangedGalaxyTags
  collections + GalaxyTagDelta record; IsEmpty + needsRebuild updated.
- Phase7Planner.Compute: diffs GalaxyTags by TagId via existing DiffById helper.
- DeploymentArtifact.ParseComposition: reads the Tags + Namespaces +
  DriverInstances arrays the ConfigComposer already emits, applies the same
  SystemPlatform filter, returns the same GalaxyTagPlan list as the composer
  so artifact-side and compose-side plans agree.
- Phase7Applier: new MaterialiseGalaxyTags pass that ensures one folder per
  distinct FolderPath then one Variable per tag. NodeId for the variable is
  "<FolderPath>.<Name>" matching the MXAccess ref so the future Galaxy
  SubscribeBulk wiring can address them directly.
- OpcUaPublishActor.RebuildAddressSpace: invokes MaterialiseGalaxyTags after
  MaterialiseHierarchy. _lastApplied initialiser updated for the new ctor.
- seed-clusters.sql: pre-existing TestMachine_001.TestAlarm001..003 rows
  needed no change — the composer/applier now picks them up automatically.

Verified end-to-end via docker-dev: deploy click → driver-a logs
"Phase7Applier: Galaxy tags materialised (tags=3, folders=1)" → OPC UA Client
CLI browses the three Variable nodes under TestMachine_001 folder. Reads
return BadWaitingForInitialData status (expected — Galaxy driver's
SubscribeBulk wiring to push values into the nodes is the remaining
follow-up).

src/Server/ZB.MOM.WW.OtOpcUa.OpcUaServer/Phase7Composer.cs

@@ -1,25 +1,40 @@
 using ZB.MOM.WW.OtOpcUa.Configuration.Entities;
+using ZB.MOM.WW.OtOpcUa.Configuration.Enums;
 
 namespace ZB.MOM.WW.OtOpcUa.OpcUaServer;
 
 /// <summary>Outcome of <see cref="Phase7Composer.Compose"/> — pure value tuple, no side effects.
 /// <see cref="UnsAreas"/> + <see cref="UnsLines"/> carry the UNS topology so the applier can
 /// materialise the Area/Line/Equipment folder hierarchy in the address space; equipment carries
-/// its parent line id so the applier knows where to hang each equipment folder.</summary>
+/// its parent line id so the applier knows where to hang each equipment folder.
+/// <see cref="GalaxyTags"/> carries SystemPlatform-namespace tags (Galaxy hierarchy) so the
+/// applier can materialise their FolderPath + Variable nodes ahead of any driver subscribe.</summary>
 public sealed record Phase7CompositionResult(
     IReadOnlyList<UnsAreaProjection> UnsAreas,
     IReadOnlyList<UnsLineProjection> UnsLines,
     IReadOnlyList<EquipmentNode> EquipmentNodes,
     IReadOnlyList<DriverInstancePlan> DriverInstancePlans,
-    IReadOnlyList<ScriptedAlarmPlan> ScriptedAlarmPlans)
+    IReadOnlyList<ScriptedAlarmPlan> ScriptedAlarmPlans,
+    IReadOnlyList<GalaxyTagPlan> GalaxyTags)
 {
-    /// <summary>Convenience constructor for tests + earlier callers that don't yet carry UNS topology.</summary>
+    /// <summary>Convenience constructor for tests + earlier callers that don't carry UNS or Galaxy data.</summary>
     public Phase7CompositionResult(
         IReadOnlyList<EquipmentNode> equipmentNodes,
         IReadOnlyList<DriverInstancePlan> driverInstancePlans,
         IReadOnlyList<ScriptedAlarmPlan> scriptedAlarmPlans)
         : this(Array.Empty<UnsAreaProjection>(), Array.Empty<UnsLineProjection>(),
-               equipmentNodes, driverInstancePlans, scriptedAlarmPlans)
+               equipmentNodes, driverInstancePlans, scriptedAlarmPlans, Array.Empty<GalaxyTagPlan>())
+    {
+    }
+
+    /// <summary>Convenience constructor for callers carrying UNS but not Galaxy data.</summary>
+    public Phase7CompositionResult(
+        IReadOnlyList<UnsAreaProjection> unsAreas,
+        IReadOnlyList<UnsLineProjection> unsLines,
+        IReadOnlyList<EquipmentNode> equipmentNodes,
+        IReadOnlyList<DriverInstancePlan> driverInstancePlans,
+        IReadOnlyList<ScriptedAlarmPlan> scriptedAlarmPlans)
+        : this(unsAreas, unsLines, equipmentNodes, driverInstancePlans, scriptedAlarmPlans, Array.Empty<GalaxyTagPlan>())
     {
     }
 }
@@ -30,6 +45,21 @@ public sealed record EquipmentNode(string EquipmentId, string DisplayName, strin
 public sealed record DriverInstancePlan(string DriverInstanceId, string DriverType, string ConfigJson);
 public sealed record ScriptedAlarmPlan(string ScriptedAlarmId, string EquipmentId, string PredicateScriptId, string MessageTemplate);
 
+/// <summary>
+///     One Galaxy / SystemPlatform-namespace tag from a <see cref="Tag"/> row where
+///     <see cref="Tag.EquipmentId"/> is null. Carries the FolderPath segment that the applier
+///     turns into a folder, the leaf <see cref="DisplayName"/> for the Variable, the OPC UA
+///     <see cref="DataType"/>, and the dot-form MXAccess reference (<see cref="MxAccessRef"/>)
+///     that the Galaxy driver consumes when subscribing.
+/// </summary>
+public sealed record GalaxyTagPlan(
+    string TagId,
+    string DriverInstanceId,
+    string FolderPath,
+    string DisplayName,
+    string DataType,
+    string MxAccessRef);
+
 /// <summary>
 /// Pure composer that flattens the live-edit DB tables into the address-space build plan a
 /// driver-role host needs. Same inputs → same outputs, no logging, no DB writes. The driver-role
@@ -43,19 +73,32 @@ public sealed record ScriptedAlarmPlan(string ScriptedAlarmId, string EquipmentI
 /// </summary>
 public static class Phase7Composer
 {
-    /// <summary>Convenience overload for legacy callers + tests that don't yet supply UNS topology.</summary>
+    /// <summary>Convenience overload for legacy callers + tests that don't yet supply UNS / Galaxy data.</summary>
     public static Phase7CompositionResult Compose(
         IReadOnlyList<Equipment> equipment,
         IReadOnlyList<DriverInstance> driverInstances,
         IReadOnlyList<ScriptedAlarm> scriptedAlarms) =>
-        Compose(Array.Empty<UnsArea>(), Array.Empty<UnsLine>(), equipment, driverInstances, scriptedAlarms);
+        Compose(Array.Empty<UnsArea>(), Array.Empty<UnsLine>(), equipment, driverInstances, scriptedAlarms,
+                Array.Empty<Tag>(), Array.Empty<Namespace>());
+
+    /// <summary>UNS-aware overload that doesn't yet supply Galaxy tags.</summary>
+    public static Phase7CompositionResult Compose(
+        IReadOnlyList<UnsArea> unsAreas,
+        IReadOnlyList<UnsLine> unsLines,
+        IReadOnlyList<Equipment> equipment,
+        IReadOnlyList<DriverInstance> driverInstances,
+        IReadOnlyList<ScriptedAlarm> scriptedAlarms) =>
+        Compose(unsAreas, unsLines, equipment, driverInstances, scriptedAlarms,
+                Array.Empty<Tag>(), Array.Empty<Namespace>());
 
     public static Phase7CompositionResult Compose(
         IReadOnlyList<UnsArea> unsAreas,
         IReadOnlyList<UnsLine> unsLines,
         IReadOnlyList<Equipment> equipment,
         IReadOnlyList<DriverInstance> driverInstances,
-        IReadOnlyList<ScriptedAlarm> scriptedAlarms)
+        IReadOnlyList<ScriptedAlarm> scriptedAlarms,
+        IReadOnlyList<Tag> tags,
+        IReadOnlyList<Namespace> namespaces)
     {
         var areas = unsAreas
             .OrderBy(a => a.UnsAreaId, StringComparer.Ordinal)
@@ -82,6 +125,30 @@ public static class Phase7Composer
             .Select(a => new ScriptedAlarmPlan(a.ScriptedAlarmId, a.EquipmentId, a.PredicateScriptId, a.MessageTemplate))
             .ToList();
 
-        return new Phase7CompositionResult(areas, lines, nodes, plans, alarms);
+        // SystemPlatform tags = Galaxy tags. Match each tag to its DriverInstance and that
+        // driver's Namespace; emit only when the namespace kind is SystemPlatform AND the tag
+        // has no EquipmentId (per the entity invariant for SystemPlatform).
+        var driversById = driverInstances.ToDictionary(d => d.DriverInstanceId, StringComparer.Ordinal);
+        var namespacesById = namespaces.ToDictionary(n => n.NamespaceId, StringComparer.Ordinal);
+
+        var galaxyTags = tags
+            .Where(t => t.EquipmentId is null)
+            .Where(t => driversById.TryGetValue(t.DriverInstanceId, out var di)
+                        && namespacesById.TryGetValue(di.NamespaceId, out var ns)
+                        && ns.Kind == NamespaceKind.SystemPlatform)
+            .OrderBy(t => t.DriverInstanceId, StringComparer.Ordinal)
+            .ThenBy(t => t.FolderPath, StringComparer.Ordinal)
+            .ThenBy(t => t.Name, StringComparer.Ordinal)
+            .Select(t => new GalaxyTagPlan(
+                TagId: t.TagId,
+                DriverInstanceId: t.DriverInstanceId,
+                FolderPath: t.FolderPath ?? string.Empty,
+                DisplayName: t.Name,
+                DataType: t.DataType,
+                // MXAccess reference: "FolderPath.Name" when FolderPath is set, else just "Name".
+                MxAccessRef: string.IsNullOrWhiteSpace(t.FolderPath) ? t.Name : $"{t.FolderPath}.{t.Name}"))
+            .ToList();
+
+        return new Phase7CompositionResult(areas, lines, nodes, plans, alarms, galaxyTags);
     }
 }