R1.1 ExecuteSqlCommandAsync (ExeC + GetR, NRBF DataTable, no BinaryFormatter)

Ship SQL command execution over the 2020 WCF aa/Retr/ExeC + aa/Retr/GetR ops:
HistorianClient.ExecuteSqlCommandAsync(sql) -> HistorianSqlResult (columns +
typed rows). String-handle ops reached with the Open2 storage-session GUID
formatted uppercase (the handle format that unlocked GETRP/GETHI).

Chain: Retr.GetV prime -> ExeC(handle, sql, option=0, ref queryHandle) ->
GetR loop. Key gotcha captured: GetR returns FALSE even on success -- the byte
stream is in pResultBuff regardless; false just signals the final page. So the
orchestrator consumes the buffer first, then stops on a false result / empty page.

GetR's pResultBuff is an NRBF-serialized System.Data.DataTable
(SerializationFormat.Xml: members XmlSchema (XSD) + XmlDiffGram (rows)).
BinaryFormatter is removed from .NET 10, so the stream is decoded read-only with
the System.Formats.Nrbf package (NrbfDecoder) + XDocument -- no BinaryFormatter,
no code execution. Values are typed per the XSD type, falling back to string.

Adds: HistorianSqlResult / HistorianSqlColumn / HistorianSqlExecuteOption models,
HistorianSqlResultProtocol (NRBF + diffgram parser), HistorianWcfSqlClient
(ExeC/GetR orchestration with an AVEVA_HISTORIAN_SQL_DUMP diagnostic), dialect +
public API. Golden WcfSqlResultProtocolTests pinned to the real clean GetR stream
for the benign "SELECT 1 AS ProbeValue" (no sensitive data); gated live tests
(single cell + multi-column/multi-row/NULL). Doc: wcf-exec-sql.md; roadmap R1.1
DONE; wall doc + memory updated (incl. the QTB-server-side nuance). 229 tests green.

Note: a raw instrument-wcf capture corrupts a large pResultBuff with MDAS
transport chunk markers (0x9F); the clean contract-level byte[] is dumped via the
AVEVA_HISTORIAN_SQL_DUMP env var for the golden fixture.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01B6mcaT2PjRFKcogzp9UkfC

src/AVEVA.Historian.Client/Protocol/Historian2020ProtocolDialect.cs

@@ -74,6 +74,13 @@ internal sealed class Historian2020ProtocolDialect
         return Wcf.HistorianWcfStatusClient.GetRuntimeParameterAsync(_options, name, cancellationToken);
     }
 
+    public Task<HistorianSqlResult> ExecuteSqlCommandAsync(string command, HistorianSqlExecuteOption option, CancellationToken cancellationToken)
+    {
+        cancellationToken.ThrowIfCancellationRequested();
+        ArgumentException.ThrowIfNullOrWhiteSpace(command);
+        return Wcf.HistorianWcfSqlClient.ExecuteSqlCommandAsync(_options, command, option, cancellationToken);
+    }
+
     private static async IAsyncEnumerable<T> Missing<T>(
         string operation,
         [System.Runtime.CompilerServices.EnumeratorCancellation] CancellationToken cancellationToken)