fix(historian): #679 Gateway — Average/Count not supported (no AVEVA equivalent), TimeAverage → TimeWeightedAverage

src/Drivers/ZB.MOM.WW.OtOpcUa.Driver.Historian.Gateway/GatewayHistorianDataSource.cs

@@ -84,8 +84,8 @@ public sealed class GatewayHistorianDataSource : IHistorianDataSource, IAsyncDis
         var mode = AggregateModeMapper.ToRetrievalMode(aggregate);
         try
         {
-            // Total/Count are now native gateway retrieval modes — no client-side scaling
-            // (unlike the Wonderware path that derived Total as Average × interval-seconds).
+            // Total is a native gateway retrieval mode (Integral) — no client-side scaling. Average and Count
+            // have no AVEVA mode and were rejected by the mapper above (#679).
             var buckets = new List<HistorianAggregateSample>();
             await foreach (var bucket in _client
                 .ReadAggregateAsync(fullReference, startUtc, endUtc, mode, interval, cancellationToken)