Resolve all high-severity architecture review findings

src/ZB.MOM.WW.ScadaBridge.DataConnectionLayer/Adapters/MxGatewayDataConnection.cs

@@ -263,7 +263,7 @@ public class MxGatewayDataConnection
     public async Task UnsubscribeAsync(string subscriptionId, CancellationToken cancellationToken = default)
     {
         if (_subs.TryRemove(subscriptionId, out var s))
-            _tagToSub.TryRemove(s.TagPath, out _);
+            ((ICollection<KeyValuePair<string, string>>)_tagToSub).Remove(new(s.TagPath, subscriptionId));
         await _client!.UnsubscribeAsync(subscriptionId, cancellationToken);
     }
 
@@ -297,7 +297,7 @@ public class MxGatewayDataConnection
         foreach (var id in subscriptionIds)
         {
             if (_subs.TryRemove(id, out var s))
-                _tagToSub.TryRemove(s.TagPath, out _);
+                ((ICollection<KeyValuePair<string, string>>)_tagToSub).Remove(new(s.TagPath, id));
         }
 
         await _client!.UnsubscribeBulkAsync(subscriptionIds, cancellationToken);

src/ZB.MOM.WW.ScadaBridge.DataConnectionLayer/Adapters/RealMxGatewayClient.cs

@@ -216,7 +216,7 @@ public sealed class RealMxGatewayClient : IMxGatewayClient
             // UnsubscribeBulk unadvises AND removes the item, releasing every advice kind.
             _supervisoryAdvised.TryRemove(handle, out _);
             if (_handleToTag.TryRemove(handle, out var tag))
-                _tagToHandle.TryRemove(tag, out _);
+                ((ICollection<KeyValuePair<string, int>>)_tagToHandle).Remove(new(tag, handle));
         }
     }
 
@@ -233,7 +233,7 @@ public sealed class RealMxGatewayClient : IMxGatewayClient
         // so forget any supervisory-advise state for this handle.
         _supervisoryAdvised.TryRemove(handle, out _);
         if (_handleToTag.TryRemove(handle, out var tag))
-            _tagToHandle.TryRemove(tag, out _);
+            ((ICollection<KeyValuePair<string, int>>)_tagToHandle).Remove(new(tag, handle));
     }
 
     /// <inheritdoc />

src/ZB.MOM.WW.ScadaBridge.DataConnectionLayer/Adapters/RealOpcUaClient.cs

@@ -68,6 +68,7 @@ public class RealOpcUaClient : IOpcUaClient
     private readonly ConcurrentDictionary<string, MonitoredItem> _alarmItems = new();
     // Per-handle "currently inside a ConditionRefresh replay" flag → Snapshot kind.
     private readonly ConcurrentDictionary<string, bool> _alarmInRefresh = new();
+    private readonly ConcurrentDictionary<string, Guid> _alarmSnapshotIds = new();
     // Per-handle last (active, acked) by source reference, to derive transition kind.
     private readonly ConcurrentDictionary<string, Dictionary<string, (bool Active, bool Acked)>> _alarmLastState = new();
     // Int flag toggled with Interlocked.Exchange so the
@@ -543,6 +544,10 @@ public class RealOpcUaClient : IOpcUaClient
         }
         _monitoredItems.Clear();
         _callbacks.Clear();
+        _alarmItems.Clear();
+        _alarmInRefresh.Clear();
+        _alarmSnapshotIds.Clear();
+        _alarmLastState.Clear();
     }
 
     /// <inheritdoc />
@@ -925,6 +930,7 @@ public class RealOpcUaClient : IOpcUaClient
             }, cancellationToken);
         }
         _alarmInRefresh.TryRemove(subscriptionHandle, out _);
+        _alarmSnapshotIds.TryRemove(subscriptionHandle, out _);
         _alarmLastState.TryRemove(subscriptionHandle, out _);
     }
 
@@ -1160,12 +1166,16 @@ public class RealOpcUaClient : IOpcUaClient
         if (eventType == ObjectTypeIds.RefreshStartEventType)
         {
             _alarmInRefresh[handle] = true;
+            var startEpoch = Guid.NewGuid();
+            _alarmSnapshotIds[handle] = startEpoch;
+            onTransition(SnapshotBoundary(AlarmTransitionKind.SnapshotStart, subscriptionSourceReference, startEpoch));
             return;
         }
         if (eventType == ObjectTypeIds.RefreshEndEventType)
         {
             _alarmInRefresh[handle] = false;
-            onTransition(SnapshotComplete());
+            if (_alarmSnapshotIds.TryRemove(handle, out var endEpoch))
+                onTransition(SnapshotBoundary(AlarmTransitionKind.SnapshotComplete, subscriptionSourceReference, endEpoch));
             return;
         }
 
@@ -1253,13 +1263,16 @@ public class RealOpcUaClient : IOpcUaClient
             LimitValue: limitValue,
             // MES alarm-status API §6.4: true source ack instant (index 18) when supplied,
             // else the observed event time; null unless the condition is active AND acked.
-            AckTime: OpcUaAlarmMapper.DeriveAckTime(active, acked, sourceAckTime, time)));
+            AckTime: OpcUaAlarmMapper.DeriveAckTime(active, acked, sourceAckTime, time),
+            SnapshotSourceReference: inRefresh ? subscriptionSourceReference ?? string.Empty : null,
+            SnapshotId: inRefresh && _alarmSnapshotIds.TryGetValue(handle, out var epoch) ? epoch : null));
     }
 
-    private static NativeAlarmTransition SnapshotComplete() => new(
-        "", "", "", AlarmTransitionKind.SnapshotComplete,
+    private static NativeAlarmTransition SnapshotBoundary(AlarmTransitionKind kind, string? source, Guid epoch) => new(
+        "", source ?? string.Empty, "", kind,
         new Commons.Types.Alarms.AlarmConditionState(false, true, null, AlarmShelveState.Unshelved, false, 0),
-        "", "", "", "", "", null, DateTimeOffset.UtcNow, "", "");
+        "", "", "", "", "", null, DateTimeOffset.UtcNow, "", "",
+        SnapshotSourceReference: source ?? string.Empty, SnapshotId: epoch);
 
     /// <summary>
     /// Nodes per OPC UA Read/Write service call. Stays under the