Point the .NET client at the StreamAlarms alarm feed

Replace the client's QueryActiveAlarmsAsync with StreamAlarmsAsync —
a session-less subscription to the gateway's central alarm feed that
yields the active-alarm snapshot followed by live transitions.
AcknowledgeAlarm is session-less (AcknowledgeAlarmRequest no longer
carries a session id). Updates the transport interface, the gRPC
transport, the test fake, and the alarm tests; the .NET client
solution builds and its alarm tests pass.

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

clients/dotnet/MxGateway.Client/GrpcMxGatewayClientTransport.cs

@@ -134,8 +134,8 @@ internal sealed class GrpcMxGatewayClientTransport(
     }
 
     /// <inheritdoc />
-    public async IAsyncEnumerable<ActiveAlarmSnapshot> QueryActiveAlarmsAsync(
-        QueryActiveAlarmsRequest request,
+    public async IAsyncEnumerable<AlarmFeedMessage> StreamAlarmsAsync(
+        StreamAlarmsRequest request,
         CallOptions callOptions,
         [System.Runtime.CompilerServices.EnumeratorCancellation] CancellationToken cancellationToken = default)
     {
@@ -143,12 +143,12 @@ internal sealed class GrpcMxGatewayClientTransport(
             ? cancellationToken
             : callOptions.CancellationToken;
 
-        using AsyncServerStreamingCall<ActiveAlarmSnapshot> call = RawClient.QueryActiveAlarms(request, callOptions);
+        using AsyncServerStreamingCall<AlarmFeedMessage> call = RawClient.StreamAlarms(request, callOptions);
 
-        IAsyncStreamReader<ActiveAlarmSnapshot> responseStream = call.ResponseStream;
+        IAsyncStreamReader<AlarmFeedMessage> responseStream = call.ResponseStream;
         while (true)
         {
-            ActiveAlarmSnapshot? snapshot;
+            AlarmFeedMessage? message;
             try
             {
                 if (!await responseStream.MoveNext(effectiveCancellationToken).ConfigureAwait(false))
@@ -156,22 +156,22 @@ internal sealed class GrpcMxGatewayClientTransport(
                     break;
                 }
 
-                snapshot = responseStream.Current;
+                message = responseStream.Current;
             }
             catch (RpcException exception)
             {
                 throw RpcExceptionMapper.Map(exception, effectiveCancellationToken);
             }
 
-            yield return snapshot;
+            yield return message;
         }
     }
 
     /// <inheritdoc />
-    IAsyncEnumerable<ActiveAlarmSnapshot> IMxGatewayClientTransport.QueryActiveAlarmsAsync(
-        QueryActiveAlarmsRequest request,
+    IAsyncEnumerable<AlarmFeedMessage> IMxGatewayClientTransport.StreamAlarmsAsync(
+        StreamAlarmsRequest request,
         CallOptions callOptions)
     {
-        return QueryActiveAlarmsAsync(request, callOptions);
+        return StreamAlarmsAsync(request, callOptions);
     }
 }