Phase 3 PR 16 — concrete OPC UA server scaffolding with AlarmConditionState materialization. Introduces the OPCFoundation.NetStandard.Opc.Ua.Server package (v1.5.374.126, same version the v1 stack already uses) and two new server-side classes: DriverNodeManager : CustomNodeManager2 is the concrete realization of PR 15's IAddressSpaceBuilder contract — Folder() creates FolderState nodes under an Organizes hierarchy rooted at ObjectsFolder > DriverInstanceId; Variable() creates BaseDataVariableState with DataType mapped from DriverDataType (Boolean/Int32/Float/Double/String/DateTime) + ValueRank (Scalar or OneDimension) + AccessLevel CurrentReadOrWrite; AddProperty() creates PropertyState with HasProperty reference. Read hook wires OnReadValue per variable to route to IReadable.ReadAsync; Write hook wires OnWriteValue to route to IWritable.WriteAsync and surface per-tag StatusCode. MarkAsAlarmCondition() materializes an OPC UA AlarmConditionState child of the variable, seeded from AlarmConditionInfo (SourceName, InitialSeverity → UA severity via Low=250/Medium=500/High=700/Critical=900, InitialDescription), initial state Enabled + Acknowledged + Inactive + Retain=false. Returns an IAlarmConditionSink whose OnTransition updates alarm.Severity/Time/Message and switches state per AlarmType string ('Active' → SetActiveState(true) + SetAcknowledgedState(false) + Retain=true; 'Acknowledged' → SetAcknowledgedState(true); 'Inactive' → SetActiveState(false) + Retain=false if already Acked) then calls alarm.ReportEvent to emit the OPC UA event to subscribed clients. Galaxy's GalaxyAlarmTracker (PR 14) now lands at a concrete AlarmConditionState node instead of just raising an unobserved C# event. OtOpcUaServer : StandardServer wires one DriverNodeManager per DriverHost.GetDriver during CreateMasterNodeManager — anonymous endpoint, no security profile (minimum-viable; LDAP + security-profile wire-up is the next PR). DriverHost gains public GetDriver(instanceId) so the server can enumerate drivers at startup. NestedBuilder inner class in DriverNodeManager implements IAddressSpaceBuilder by temporarily retargeting the parent's _currentFolder during each call so Folder→Variable→AddProperty land under the correct subtree — not thread-safe if discovery ran concurrently, but GenericDriverNodeManager.BuildAddressSpaceAsync is sequential per driver so this is safe by construction. NuGet audit suppress for GHSA-h958-fxgg-g7w3 (moderate-severity in OPCFoundation.NetStandard.Opc.Ua.Core 1.5.374.126; v1 stack already accepts this risk on the same package version). PR 16 is scoped as scaffolding — the actual server startup (ApplicationInstance, certificate config, endpoint binding, session management wiring into OpcUaServerService.ExecuteAsync) is deferred to a follow-up PR because it needs ApplicationConfiguration XML + optional-cert-store logic that depends on per-deployment policy decisions. The materialization shape is complete: a subsequent PR adds 100 LOC to start the server and all the already-written IAddressSpaceBuilder + alarm-condition + read/write wire-up activates end-to-end. Full solution: 0 errors, 152 unit tests pass (no new tests this PR — DriverNodeManager unit testing needs an IServerInternal mock which is heavyweight; live-endpoint integration tests land alongside the server-startup PR).

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

src/ZB.MOM.WW.OtOpcUa.Core/Hosting/DriverHost.cs

@@ -24,6 +24,17 @@ public sealed class DriverHost : IAsyncDisposable
             return _drivers.TryGetValue(driverInstanceId, out var d) ? d.GetHealth() : null;
     }
 
+    /// <summary>
+    ///     Look up a registered driver by instance id. Used by the OPC UA server runtime
+    ///     (<c>OtOpcUaServer</c>) to instantiate one <c>DriverNodeManager</c> per driver at
+    ///     startup. Returns null when the driver is not registered.
+    /// </summary>
+    public IDriver? GetDriver(string driverInstanceId)
+    {
+        lock (_lock)
+            return _drivers.TryGetValue(driverInstanceId, out var d) ? d : null;
+    }
+
     /// <summary>
     ///     Registers the driver and calls <see cref="IDriver.InitializeAsync"/>. If initialization
     ///     throws, the driver is kept in the registry so the operator can retry; quality on its