gRPC M0 R0.2: tag metadata over gRPC (GetTagInfosFromName, live-verified)

Routes HistorianClient.GetTagMetadataAsync over gRPC when Transport==RemoteGrpc,
via the new Grpc/HistorianGrpcTagClient calling RetrievalService.GetTagInfosFromName
(the plural string-handle metadata op).

- String handle = the Open2 storage-session GUID formatted uppercase (the format
  that resolves the native string-handle path); threaded out of the shared handshake
  via a new HistorianGrpcHandshake.Session { ClientHandle, StorageSessionId, StringHandle }.
- Request btTagNames = uint count + per-name(uint charCount + UTF-16LE) — golden-byte
  unit-tested (BuildTagNamesBuffer).
- Response btTagInfos = uint count + CTagMetadata records — decoded by the existing
  HistorianTagQueryProtocol.ParseGetTagInfoResponse; data type via the shared MapDataType.

The 2020 WCF string-handle wall does NOT apply on the gRPC front door, as the
string-handle-wall RE note predicted. LIVE-VERIFIED against a real 2023 R2 server:
GetTagMetadataAsync returns the requested tag with a valid decoded data type.

216 unit tests pass. Captured framing confirmed live then discarded; no tag names
or identities committed.

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

src/AVEVA.Historian.Client/HistorianClient.cs

@@ -104,7 +104,9 @@ public sealed class HistorianClient : IAsyncDisposable
     public Task<HistorianTagMetadata?> GetTagMetadataAsync(string tag, CancellationToken cancellationToken = default)
     {
         ArgumentException.ThrowIfNullOrWhiteSpace(tag);
-        return HistorianWcfTagClient.GetTagMetadataAsync(_options, tag, cancellationToken);
+        return _options.Transport == HistorianTransport.RemoteGrpc
+            ? Grpc.HistorianGrpcTagClient.GetTagMetadataAsync(_options, tag, cancellationToken)
+            : HistorianWcfTagClient.GetTagMetadataAsync(_options, tag, cancellationToken);
     }
 
     public Task<HistorianConnectionStatus> GetConnectionStatusAsync(CancellationToken cancellationToken = default)