Merge re/r1.4-gethi-finding: R1.1 ExecuteSqlCommand + R1.4 GetHistorianInfo (bounded)

# Conflicts:
#	docs/plans/hcal-roadmap.md
#	src/AVEVA.Historian.Client/HistorianClient.cs
#	src/AVEVA.Historian.Client/Protocol/Historian2020ProtocolDialect.cs
#	tests/AVEVA.Historian.Client.Tests/HistorianClientIntegrationTests.cs
#	tools/AVEVA.Historian.NativeTraceHarness/Program.cs

tests/AVEVA.Historian.Client.Tests/HistorianClientIntegrationTests.cs

@@ -331,6 +331,65 @@ public sealed class HistorianClientIntegrationTests
         });
     }
 
+    [Fact]
+    public async Task ExecuteSqlCommandAsync_AgainstLocalHistorian_ReturnsRecordSet()
+    {
+        string? host = Environment.GetEnvironmentVariable("HISTORIAN_HOST");
+        if (string.IsNullOrWhiteSpace(host) || !string.Equals(host, "localhost", StringComparison.OrdinalIgnoreCase) || !OperatingSystem.IsWindows())
+        {
+            return;
+        }
+
+        HistorianClient client = new(new HistorianClientOptions
+        {
+            Host = host,
+            IntegratedSecurity = true,
+            Transport = HistorianTransport.LocalPipe
+        });
+
+        // ExeC/GetR ride the storage-session GUID as an uppercase string handle. A constant SELECT
+        // returns a single int column; the DataTable is decoded from the NRBF stream (no BinaryFormatter).
+        AVEVA.Historian.Client.Models.HistorianSqlResult result =
+            await client.ExecuteSqlCommandAsync("SELECT 1 AS ProbeValue", cancellationToken: CancellationToken.None);
+
+        AVEVA.Historian.Client.Models.HistorianSqlColumn column = Assert.Single(result.Columns);
+        Assert.Equal("ProbeValue", column.Name);
+        IReadOnlyList<object?> row = Assert.Single(result.Rows);
+        Assert.Equal(1, Assert.Single(row));
+    }
+
+    [Fact]
+    public async Task ExecuteSqlCommandAsync_AgainstLocalHistorian_MultiColumnMultiRow()
+    {
+        string? host = Environment.GetEnvironmentVariable("HISTORIAN_HOST");
+        if (string.IsNullOrWhiteSpace(host) || !string.Equals(host, "localhost", StringComparison.OrdinalIgnoreCase) || !OperatingSystem.IsWindows())
+        {
+            return;
+        }
+
+        HistorianClient client = new(new HistorianClientOptions
+        {
+            Host = host,
+            IntegratedSecurity = true,
+            Transport = HistorianTransport.LocalPipe
+        });
+
+        // Fully synthetic query (no server data): two columns (int + string), two rows, one NULL —
+        // exercises the schema/diffgram parser beyond the single-cell case.
+        AVEVA.Historian.Client.Models.HistorianSqlResult result = await client.ExecuteSqlCommandAsync(
+            "SELECT 10 AS Num, 'alpha' AS Word UNION ALL SELECT 20, NULL",
+            cancellationToken: CancellationToken.None);
+
+        Assert.Equal(2, result.Columns.Count);
+        Assert.Equal("Num", result.Columns[0].Name);
+        Assert.Equal("Word", result.Columns[1].Name);
+        Assert.Equal(2, result.Rows.Count);
+        Assert.Equal(10, result.Rows[0][0]);
+        Assert.Equal("alpha", result.Rows[0][1]);
+        Assert.Equal(20, result.Rows[1][0]);
+        Assert.Null(result.Rows[1][1]);
+    }
+
     [Fact]
     public async Task GetConnectionStatusAsync_AgainstLocalHistorian_ReportsConnectedToServer()
     {