fix(store-and-forward): inline ordered replication dispatch; Warning + counter on replication failures

src/ZB.MOM.WW.ScadaBridge.Commons/Observability/ScadaBridgeTelemetry.cs

@@ -37,6 +37,11 @@ public static class ScadaBridgeTelemetry
         Meter.CreateCounter<long>("scadabridge.inbound_api.requests", unit: "1",
             description: "Inbound API requests, tagged by method.");
 
+    /// <summary>Incremented each time an S&amp;F buffer replication op fails to dispatch/deliver to the peer.</summary>
+    private static readonly Counter<long> _replicationFailures =
+        Meter.CreateCounter<long>("scadabridge.store_and_forward.replication.failures", unit: "1",
+            description: "S&F buffer replication operations that failed to dispatch/deliver to the peer node");
+
     // ---------------- Observable gauges ----------------
 
     /// <summary>Current count of open site connections, mutated via <see cref="Interlocked"/>.</summary>
@@ -70,6 +75,9 @@ public static class ScadaBridgeTelemetry
     public static void RecordInboundApiRequest(string method) =>
         _inboundApiRequests.Add(1, new KeyValuePair<string, object?>("method", method));
 
+    /// <summary>Records one failed S&amp;F replication dispatch.</summary>
+    public static void RecordReplicationFailure() => _replicationFailures.Add(1);
+
     /// <summary>Records that a site connection opened (increments the up-count gauge).</summary>
     public static void SiteConnectionOpened() => Interlocked.Increment(ref _siteConnectionsUp);