Add 2023 R2 gRPC transport (RemoteGrpc) reusing native byte payloads

Stands up HistorianTransport.RemoteGrpc end-to-end for the read path,
built on the recovered 2023 R2 gRPC contract (gRPC-Web/HTTP-1.1, port
32565, gzip). The opaque protobuf `bytes` fields carry the SAME native
binary payloads as the 2020 WCF/MDAS path, so the proven serializers and
parsers are reused unchanged.

- Grpc/Protos/*.proto: 6 protoc-validated contracts recovered from
  embedded FileDescriptors (authoritative, not guessed).
- Grpc/HistorianGrpcChannelFactory: GrpcWebHandler/HTTP-1.1 channel,
  ResolvePort/ResolveAddress, optional TLS + gzip.
- Grpc/HistorianGrpcReadOrchestrator: mirrors the WCF read chain over
  gRPC; auth uses HistoryService.ExchangeKey (the gRPC ValCl op).
- Wcf/HistorianNativeHandshake: transport-agnostic Open2 request builder
  + SSPI/Negotiate token loop + response decode, shared by WCF and gRPC.
- Op map (2020 -> gRPC): ValCl->ExchangeKey, Open2->OpenConnection,
  StartQuery2->StartQuery, GetNextQueryResultBuffer2->GetNextQueryResultBuffer.
- HistorianClientOptions: DefaultGrpcPort=32565, GrpcUseTls.
- csproj: Google.Protobuf, Grpc.Net.Client(.Web), Grpc.Tools codegen.

Not yet live-verified against a 2023 R2 server: ExchangeKey is the first
thing to revisit if a live server rejects the handshake; the inner byte
payloads are the proven 2020 protocol. Gated live test via
HISTORIAN_GRPC_HOST. 188 unit tests green; build clean.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

src/AVEVA.Historian.Client/Grpc/Protos/TransactionService.proto

@@ -0,0 +1,92 @@
+// Recovered from TransactionService.proto (AVEVA Historian SDK 2023 R2, Archestra.Grpc.Contract).
+// Reconstructed from the embedded protobuf FileDescriptor; field numbers are authoritative.
+syntax = "proto3";
+
+import "Status.proto";
+
+option csharp_namespace = "ArchestrA.Grpc.Contract.Transaction";
+
+message ForwardSnapshotRequest {
+  string strHandle = 1;
+  string strSessionID = 2;
+  uint32 queryID = 3;
+  uint64 snapShotChunkOffset = 4;
+  bytes btInput = 5;
+}
+
+message ForwardSnapshotResponse {
+  .Status status = 1;
+}
+
+message ForwardSnapshotBeginRequest {
+  string strHandle = 1;
+  uint64 totalSize = 2;
+  uint64 startTime = 3;
+  uint64 endTime = 4;
+}
+
+message ForwardSnapshotBeginResponse {
+  string strSessionID = 1;
+  uint32 queryID = 2;
+  .Status status = 3;
+}
+
+message ForwardSnapshotEndRequest {
+  string strHandle = 1;
+  string strSessionID = 2;
+  uint32 queryID = 3;
+  bytes timeRange = 4;
+}
+
+message ForwardSnapshotEndResponse {
+  bytes tagIds = 1;
+  .Status status = 2;
+}
+
+message GetTransactionInterfaceVersionRequest {
+}
+
+message GetTransactionInterfaceVersionResponse {
+  uint32 error = 1;
+  uint32 version = 2;
+}
+
+message AddNonStreamValuesBeginRequest {
+  string strHandle = 1;
+}
+
+message AddNonStreamValuesBeginResponse {
+  .Status status = 1;
+  string strTransactionId = 2;
+}
+
+message AddNonStreamValuesRequest {
+  string strHandle = 1;
+  string strTransactionId = 2;
+  bytes btInput = 3;
+}
+
+message AddNonStreamValuesResponse {
+  .Status status = 1;
+}
+
+message AddNonStreamValuesEndRequest {
+  string strHandle = 1;
+  string strTransactionId = 2;
+  bool bCommit = 3;
+}
+
+message AddNonStreamValuesEndResponse {
+  .Status status = 1;
+}
+
+service TransactionService {
+  rpc ForwardSnapshot (.ForwardSnapshotRequest) returns (.ForwardSnapshotResponse);
+  rpc ForwardSnapshotBegin (.ForwardSnapshotBeginRequest) returns (.ForwardSnapshotBeginResponse);
+  rpc ForwardSnapshotEnd (.ForwardSnapshotEndRequest) returns (.ForwardSnapshotEndResponse);
+  rpc GetTransactionInterfaceVersion (.GetTransactionInterfaceVersionRequest) returns (.GetTransactionInterfaceVersionResponse);
+  rpc AddNonStreamValuesBegin (.AddNonStreamValuesBeginRequest) returns (.AddNonStreamValuesBeginResponse);
+  rpc AddNonStreamValues (.AddNonStreamValuesRequest) returns (.AddNonStreamValuesResponse);
+  rpc AddNonStreamValuesEnd (.AddNonStreamValuesEndRequest) returns (.AddNonStreamValuesEndResponse);
+}
+