feat(commons): IAlarmSubscribableConnection seam + DCL native alarm messages

src/ZB.MOM.WW.ScadaBridge.Commons/Messages/DataConnection/NativeAlarmMessages.cs

@@ -0,0 +1,13 @@
+using ZB.MOM.WW.ScadaBridge.Commons.Types.Alarms;
+
+namespace ZB.MOM.WW.ScadaBridge.Commons.Messages.DataConnection;
+
+/// <summary>DCL → instance: a native alarm transition routed by source reference.</summary>
+public record NativeAlarmTransitionUpdate(string ConnectionName, NativeAlarmTransition Transition);
+
+/// <summary>
+/// DCL → instance: the alarm feed for a source became unavailable (connection
+/// lost). Consumers mark their mirrored alarms uncertain rather than clearing
+/// them; the reconnect snapshot reconciles state.
+/// </summary>
+public record NativeAlarmSourceUnavailable(string ConnectionName, string SourceReference, DateTimeOffset Timestamp);

src/ZB.MOM.WW.ScadaBridge.Commons/Messages/DataConnection/SubscribeAlarmsRequest.cs

@@ -0,0 +1,30 @@
+namespace ZB.MOM.WW.ScadaBridge.Commons.Messages.DataConnection;
+
+/// <summary>
+/// Sent by a NativeAlarmActor (via the DCL manager) to subscribe an instance to
+/// native alarms for a source binding. The DataConnectionActor opens one alarm
+/// feed per connection and routes transitions by source-object reference.
+/// </summary>
+public record SubscribeAlarmsRequest(
+    string CorrelationId,
+    string InstanceUniqueName,
+    string ConnectionName,
+    string SourceReference,
+    string? ConditionFilter,
+    DateTimeOffset Timestamp);
+
+/// <summary>Reply to a <see cref="SubscribeAlarmsRequest"/>.</summary>
+public record SubscribeAlarmsResponse(
+    string CorrelationId,
+    string InstanceUniqueName,
+    bool Success,
+    string? ErrorMessage,
+    DateTimeOffset Timestamp);
+
+/// <summary>Cancels a native alarm subscription for an instance + source.</summary>
+public record UnsubscribeAlarmsRequest(
+    string CorrelationId,
+    string InstanceUniqueName,
+    string ConnectionName,
+    string SourceReference,
+    DateTimeOffset Timestamp);