feat(historian): Gateway serves the per-sample aggregates from raw reads with the shared Sql.Common evaluator (#681)

Average, Count, Minimum, Maximum, Range, Start, End, Delta and Minimum/MaximumActualTime are evaluated
on the Gateway backend from forward ReadRaw reads with BucketPlan + AggregateEvaluator, so Gateway
matches SqlServer/QuestDB exactly (values, status bits, interval-start stamps, #677 reverse).

- Window read [start - 1 ms, end] so AVEVA's initial-value row never lands in a bucket; a pre-window
  row proves earlier data only with a non-Bad OPC quality (histsdk puts a value on every NULL row).
- Earlier data otherwise from a 2-row [1970, start) probe; later data from a 2-row [end, now+1d]
  look-ahead; both ignore rows stamped at their query start/end.
- No gateway stream is ever abandoned (a client-side cancel makes the gateway evict its shared
  historian session); past ServerHistorian:MaxTimeWeightedRawRows the bounded stream is drained, then
  BadTooManyOperations. The gateway's max_values-ceiling InvalidArgument maps to the same limit; a
  caller cancellation is not a backend fault.
- TimeAverage/Total stay AVEVA-native (no prior-sample read for exact Part 13 bounds), now stamped with
  the interval start (PENDING the live leg: histsdk's tail+43 start_time field is unverified) and
  carrying the Calculated bits.
- Served set: GatewayHistorianDataSource.ServedAggregates (12). Live AVEVA leg open (VPN).

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

@@ -1,5 +1,6 @@
 using ZB.MOM.WW.HistorianGateway.Contracts.Grpc;
 using ZB.MOM.WW.OtOpcUa.Core.Abstractions;
+using ZB.MOM.WW.OtOpcUa.Driver.Historian.Sql.Common;
 
 namespace ZB.MOM.WW.OtOpcUa.Driver.Historian.Gateway.Mapping;
 
@@ -30,16 +31,23 @@ internal static class SampleMapper
         else
             value = null;
 
+        return new DataValueSnapshot(
+            Value: value,
+            StatusCode: ToStatus(sample),
+            SourceTimestampUtc: sample.Timestamp?.ToDateTime(),  // Utc kind
+            ServerTimestampUtc: DateTime.UtcNow);
+    }
+
+    /// <summary>The OPC UA status of a raw sample (shared by raw reads and the #681 raw-evaluated aggregates).</summary>
+    /// <param name="sample">The gateway raw sample.</param>
+    /// <returns>The mapped status code.</returns>
+    public static uint ToStatus(HistorianSample sample)
+    {
         // Prefer the OPC DA quality byte (opc_quality); the gateway populates it directly from the
         // SDK's OpcQuality, so it is the authoritative byte for GatewayQualityMapper. Fall back to
         // the historian quality field only when opc_quality is unset (0).
         byte qualityByte = sample.OpcQuality != 0 ? (byte)sample.OpcQuality : (byte)sample.Quality;
-
-        return new DataValueSnapshot(
-            Value: value,
-            StatusCode: GatewayQualityMapper.Map(qualityByte),
-            SourceTimestampUtc: sample.Timestamp?.ToDateTime(),  // Utc kind
-            ServerTimestampUtc: DateTime.UtcNow);
+        return GatewayQualityMapper.Map(qualityByte);
     }
 
     /// <summary>Maps a batch of raw samples to value snapshots, in order.</summary>
@@ -57,20 +65,28 @@ internal static class SampleMapper
     /// <param name="aggregate">The gateway aggregate sample.</param>
     /// <returns>The driver-agnostic snapshot.</returns>
     /// <remarks>
+    /// <para>
     /// Unlike the legacy Wonderware DTO (a nullable <c>double?</c>), the gateway proto carries a
     /// non-optional <c>double value</c>, so an unavailable (no-data) bucket cannot be signalled by a
     /// null value. Instead it is signalled by a non-Good <c>opc_quality</c>: a Good bucket
     /// (<c>opc_quality &gt;= 192</c>) yields its value with a Good status, anything else maps to
     /// <c>BadNoData</c> with a null value — preserving the Wonderware aggregate contract (binary
     /// Good-with-value / BadNoData-null).
+    /// </para>
+    /// <para>
+    /// #681: both statuses carry the Calculated info bits (<c>0x401</c>) like every other backend's processed value, and
+    /// the bucket is stamped with its interval START (Part 13; it was the interval end), falling back to the end only when
+    /// the start is absent. Pending the live leg: histsdk decodes <c>start_time</c> from a row field (<c>tail + 43</c>) its
+    /// reverse-engineering notes still mark unverified.
+    /// </para>
     /// </remarks>
     public static DataValueSnapshot ToAggregateSnapshot(HistorianAggregateSample aggregate)
     {
         bool hasData = aggregate.OpcQuality >= GoodQualityFloor;
         return new DataValueSnapshot(
             Value: hasData ? aggregate.Value : null,                 // boxes as System.Double when present
-            StatusCode: hasData ? StatusGood : StatusBadNoData,
-            SourceTimestampUtc: (aggregate.EndTime ?? aggregate.StartTime)?.ToDateTime(),  // bucket timestamp
+            StatusCode: HistorianInfoBits.WithCalculated(hasData ? StatusGood : StatusBadNoData),
+            SourceTimestampUtc: (aggregate.StartTime ?? aggregate.EndTime)?.ToDateTime(),  // bucket timestamp = interval start
             ServerTimestampUtc: DateTime.UtcNow);
     }