gRPC 2023 R2: fix auth handshake op routing + accept History v12

First live-verified gRPC read against a real 2023 R2 Historian. The handshake
previously failed at round 0 (cred-independent) because the SSPI/Negotiate token
loop was routed to HistoryService.ExchangeKey. ExchangeKey is a separate
key-exchange/cert-path op, not the Negotiate loop — the token loop belongs on
StorageService.ValidateClientCredential, which kept the 2020 inBuff/outBuff token
framing the SDK's WrapValidateClientCredentialToken/TryRead helpers already build.

Captured + diffed against the recovered 2023 R2 protobuf contract and the
decompiled stock client; routing the loop to ValidateClientCredential completes
the full chain (ValidateClientCredential x N -> OpenConnection -> StartQuery ->
GetNextQueryResultBuffer) and returns rows.

- HistorianGrpcReadOrchestrator: token loop now calls
  StorageService.ValidateClientCredential(Handle, InBuff); corrected the op-map
  doc comment (was asserting the wrong ExchangeKey mapping).
- HistorianServerVersionGate: accept History interface version 12 alongside 11.
  Live server reports History=12, Retrieval=4, Storage=4; the buffers are
  byte-identical (a live read returns rows), so 12 is buffer-compatible. Retrieval
  stays pinned at 4 (matches). New AcceptedVersions() supports multi-version gates.
- New HistorianGrpcHandshakeRoutingTests: IL-level structural guardrail that
  disassembles the orchestrator (incl. lambda closures) and asserts the handshake
  invokes ValidateClientCredential and never ExchangeKey — fails if the regression
  returns.
- Updated gate tests + CLAUDE.md gRPC op-map.

240 unit tests pass on the full stack; 210 on this branch's base. The byte
payloads remain the proven 2020 protocol.

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

CLAUDE.md

@@ -71,7 +71,7 @@ Three layered subsystems, intentionally decoupled so protocol parsing can be uni
 - **`Wcf/`** — managed WCF/MDAS layer. The Historian uses Net.TCP on port `32568` with a custom `application/x-mdas` content type wrapping a binary SOAP 1.2 / WS-Addressing 1.0 envelope. `MdasMessageEncoder` + `MdasMessageEncodingBindingElement` implement that wrapper. `HistorianWcfBindingFactory` produces three flavors: plain MDAS, MDAS+Windows transport (used for `/Hist-Integrated`), and MDAS+certificate (used for `/HistCert`). Service paths live in `HistorianWcfServiceNames`. WCF data contracts (`Wcf/Contracts/`) are reproduced from server-side static analysis and are versioned per native interface (e.g., `IRetrievalServiceContract2..4`).
 - **`Protocol/`** — binary frame layer (`HistorianFrameReader`/`Writer`, `HistorianBinaryPrimitives`, `HistorianMessageType`). `Historian2020ProtocolDialect` is the version-anchored bridge between `HistorianClient` and the frame layer; methods without sufficient evidence throw `ProtocolEvidenceMissingException` rather than guessing wire bytes.
 - **`Transport/`** — pluggable `IHistorianTransport` (default: TCP). Tests inject a fake transport.
-- **`Grpc/`** — 2023 R2 gRPC transport (`HistorianTransport.RemoteGrpc`). The recovered protobuf contract lives in `Grpc/Protos/*.proto` and is compiled to client stubs at build time by `Grpc.Tools`. `HistorianGrpcChannelFactory` builds a gRPC-Web/HTTP-1.1 channel (default port `32565`, optional TLS, gzip) matching the stock 2023 R2 client. `HistorianGrpcReadOrchestrator` mirrors `HistorianWcfReadOrchestrator` but over gRPC: it reuses the exact native serializers/parsers — the same Open2 buffer, SSPI/NTLM tokens, and `DataQueryRequest`/result buffers travel inside protobuf `bytes` fields. The 2020→gRPC op map: `Hist.ValCl`→`HistoryService.ExchangeKey`, `Hist.Open2`→`HistoryService.OpenConnection`, `Retr.StartQuery2`→`RetrievalService.StartQuery`, `Retr.GetNextQueryResultBuffer2`→`RetrievalService.GetNextQueryResultBuffer`. The transport-agnostic handshake (Open2 request builder + SSPI token loop + response decode) is shared via `Wcf/HistorianNativeHandshake`. **Not yet live-verified against a 2023 R2 server** — the auth handshake op (`ExchangeKey`) is the first thing to revisit if a live server rejects it; the byte payloads are the proven 2020 protocol. Gated live test: set `HISTORIAN_GRPC_HOST` (+ `HISTORIAN_TEST_TAG`, optional `HISTORIAN_GRPC_PORT`/`HISTORIAN_GRPC_TLS`/`HISTORIAN_GRPC_DNSID`).
+- **`Grpc/`** — 2023 R2 gRPC transport (`HistorianTransport.RemoteGrpc`). The recovered protobuf contract lives in `Grpc/Protos/*.proto` and is compiled to client stubs at build time by `Grpc.Tools`. `HistorianGrpcChannelFactory` builds a gRPC-Web/HTTP-1.1 channel (default port `32565`, optional TLS, gzip) matching the stock 2023 R2 client. `HistorianGrpcReadOrchestrator` mirrors `HistorianWcfReadOrchestrator` but over gRPC: it reuses the exact native serializers/parsers — the same Open2 buffer, SSPI/NTLM tokens, and `DataQueryRequest`/result buffers travel inside protobuf `bytes` fields. The 2020→gRPC op map: `Hist.ValCl`→`StorageService.ValidateClientCredential` (the SSPI/Negotiate token loop), `Hist.Open2`→`HistoryService.OpenConnection`, `Retr.StartQuery2`→`RetrievalService.StartQuery`, `Retr.GetNextQueryResultBuffer2`→`RetrievalService.GetNextQueryResultBuffer`. The transport-agnostic handshake (Open2 request builder + SSPI token loop + response decode) is shared via `Wcf/HistorianNativeHandshake`. **Live-verified 2026-06-21 against a real 2023 R2 server** (interface versions History=12, Retrieval=4, Storage=4): the full read chain returns rows. NOTE: `HistoryService.ExchangeKey` is a SEPARATE key-exchange/cert-path op, NOT the Negotiate loop — an earlier revision wrongly routed the token loop there and it was rejected at round 0 regardless of credentials; the loop belongs on `StorageService.ValidateClientCredential` (which kept the 2020 inBuff/outBuff token framing). The byte payloads are the proven 2020 protocol and transfer unchanged; only the History interface integer differs (12 vs 11) and is buffer-compatible, so `VerifyServerInterfaceVersion=false` is currently required against a v12 server (the gate still pins History=11). Gated live test: set `HISTORIAN_GRPC_HOST` (+ `HISTORIAN_TEST_TAG`, optional `HISTORIAN_GRPC_PORT`/`HISTORIAN_GRPC_TLS`/`HISTORIAN_GRPC_DNSID`); reach the live 2023 R2 box via [[reference_2023r2_live_server_access]].
 - **`Models/`** — public DTOs and enums (`HistorianSample`, `RetrievalMode`, etc.). `HistorianDataValue` represents the discriminated value type.
 
 `InternalsVisibleTo` exposes internals to the test assembly and the reverse-engineering tool.