feat(grpc-events): handle-capture cycle — event-row gap proven NOT a client payload issue

Extends the instrument-grpc rewrite to log string (strHandle) + uint (uiHandle /
queryRequestType) params, not just byte[], and captures our SDK's live v8
openParameters for a byte-diff against the native.

Result of the exhaustive comparison (all live-confirmed via the opt-in
EventReadDiagnostic test):
- StartEventQuery request: byte-identical to the native (v6 layout)
- v8 OpenConnection openParameters: byte-identical to the native (302B) once
  ClientNodeName matches — every control byte/ConnectionType/token/ShardId
- handle usage identical: ExchangeKey->contextKey, registration->storage GUID
  (strHandle), query->client uint (uiHandle); handles valid (RTag/EnsT=True)
- queryRequestType=3, registration order, gzip metadata header — all match
- window has events (native returns 50 now); eventCount not it

Every observable client-side byte matches the native, yet the server scopes 0
events to our connection. The event RPCs succeed over our transport and return a
valid EMPTY result (not a transport error), so this is a connection/server-level
difference (session affinity tied to the native Grpc.Core HTTP/2 connection or a
connection identity used to scope events) — invisible to and unfixable by client
payload matching. Needs server-side insight, not more wire RE.

Added opt-in diagnostics (RegistrationDiag, LastResultBufferHex,
LastEventOpenRequestHex). 326/326 offline; gated test still pins the no-row throw.

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

src/AVEVA.Historian.Client/Grpc/HistorianGrpcEventOrchestrator.cs

@@ -306,7 +306,7 @@ internal sealed class HistorianGrpcEventOrchestrator
         }
 
         uint queryHandle = startResponse.UiQueryHandle;
-        RegistrationDiag += $"QH={queryHandle} clientH={session.ClientHandle} SEQresp={Convert.ToHexString(startResponse.BtResonse?.ToByteArray() ?? [])}; ";
+        RegistrationDiag += $"QH={queryHandle} clientH={session.ClientHandle} strH={session.StringHandle}; ";
         try
         {
             List<HistorianEvent> events = [];

src/AVEVA.Historian.Client/Grpc/HistorianGrpcHandshake.cs

@@ -21,6 +21,9 @@ namespace AVEVA.Historian.Client.Grpc;
 /// </summary>
 internal static class HistorianGrpcHandshake
 {
+    /// <summary>Diagnostic: hex of the most recent v8 event-connection OpenConnection request.</summary>
+    internal static string LastEventOpenRequestHex { get; private set; } = string.Empty;
+
     /// <summary>
     /// The handles produced by a successful OpenConnection. <see cref="ClientHandle"/> is the
     /// transient <c>uint</c> session token used by StartQuery/GetSystemParameter and the other
@@ -121,6 +124,7 @@ internal static class HistorianGrpcHandshake
         byte[] open2Request = eventConnection
             ? HistorianNativeHandshake.BuildEventOpenConnectionVersion8Request(contextKey, options.UserName, eventToken)
             : HistorianNativeHandshake.BuildOpenConnection3Request(options.Host, contextKey, connectionMode);
+        if (eventConnection) { LastEventOpenRequestHex = Convert.ToHexString(open2Request); }
 
         GrpcHistory.OpenConnectionResponse open2 = historyClient.OpenConnection(
             new GrpcHistory.OpenConnectionRequest { BtConnectionRequest = ByteString.CopyFrom(open2Request) },