feat(grpc): add RunRawQueryOnSession seam for handshake-reuse spike

src/AVEVA.Historian.Client/Grpc/HistorianGrpcReadOrchestrator.cs

@@ -102,12 +102,28 @@ internal sealed class HistorianGrpcReadOrchestrator
         }
     }
 
+    // Spike/Phase-1 seam (pending.md A1): run a raw query against an EXTERNALLY-supplied, already-
+    // authenticated connection + client handle — i.e. NO Create()/handshake here. RunRawChain delegates
+    // to this so the per-call path and the reuse path share one query implementation (DRY). The handshake
+    // reuse-probe test drives this directly to measure whether the server honors a reused session.
+    internal List<HistorianSample> RunRawQueryOnSession(
+        HistorianGrpcConnection connection,
+        uint clientHandle,
+        string tag,
+        DateTime startUtc,
+        DateTime endUtc,
+        int maxValues,
+        CancellationToken cancellationToken)
+    {
+        HistorianDataQueryRequest request = HistorianWcfReadOrchestrator.BuildDataQueryRequest(tag, startUtc, endUtc, maxValues);
+        return RunQuery(connection, clientHandle, request, maxValues, cancellationToken);
+    }
+
     private List<HistorianSample> RunRawChain(string tag, DateTime startUtc, DateTime endUtc, int maxValues, CancellationToken cancellationToken)
     {
         using HistorianGrpcConnection connection = HistorianGrpcChannelFactory.Create(_options);
         uint clientHandle = OpenAuthenticatedConnection(connection, cancellationToken);
-        HistorianDataQueryRequest request = HistorianWcfReadOrchestrator.BuildDataQueryRequest(tag, startUtc, endUtc, maxValues);
-        return RunQuery(connection, clientHandle, request, maxValues, cancellationToken);
+        return RunRawQueryOnSession(connection, clientHandle, tag, startUtc, endUtc, maxValues, cancellationToken);
     }
 
     private List<HistorianAggregateSample> RunAggregateChain(