feat(grpc-events): native-match event registration + skip ValidateClientCredential; diagnostics

Continues closing the event-row gap after the v8 ExchangeKey/RC4 auth breakthrough.

- HistorianGrpcHandshake: the v8 EVENT path skips StorageService.ValidateClientCredential
  (the native event connection authenticates purely via ExchangeKey + the RC4 token;
  running the Negotiate loop establishes a different session scope).
- HistorianGrpcEventOrchestrator.RegisterCmEventTag: simplified to the exact native
  gRPC event sequence (UpdateClientStatus -> RegisterTags -> EnsureTags -> GetHistorianInfo
  -> GetSystemParameter x7), dropping the 2020-WCF-era cross-service GetV probes and
  params-before-register that the gRPC event flow does not use. eventCount 5 -> 100.
- Opt-in diagnostics (RegistrationDiag, LastResultBufferHex/LastErrorBufferHex; gated
  EventReadDiagnostic test) for the continued investigation.

STATUS: auth + StartEventQuery + registration all succeed live (RTag/EnsT=True, valid
query handle), but GetNext returns version-11 rowCount-0 while the native returns 50 for
a BYTE-IDENTICAL request. Every observable wire element matches the native. The remaining
unknown is the string/uint HANDLE field VALUES the native uses per event RPC — the
instrument-grpc capture logged only byte[] params, not the handle fields. Next: extend
the IL rewrite to log strHandle/uiHandle/queryRequestType, re-capture, and match.
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

tests/AVEVA.Historian.Client.Tests/HistorianGrpcIntegrationTests.cs

@@ -533,7 +533,7 @@ public sealed class HistorianGrpcIntegrationTests
         string outcome;
         try
         {
-            await foreach (HistorianEvent evt in orch.ReadEventsAsync(DateTime.UtcNow.AddDays(-30), DateTime.UtcNow, null, CancellationToken.None))
+            await foreach (HistorianEvent evt in orch.ReadEventsAsync(DateTime.UtcNow.AddDays(-90), DateTime.UtcNow, null, CancellationToken.None))
             {
                 events.Add(evt);
                 if (events.Count >= 3) { break; }
@@ -546,7 +546,8 @@ public sealed class HistorianGrpcIntegrationTests
         }
 
         throw new Xunit.Sdk.XunitException(
-            $"[DIAG] outcome={outcome} | events={events.Count} | LastResultLen={orch.LastResultBufferLength} | LastErr='{orch.LastErrorBufferDescription}'");
+            $"[DIAG] outcome={outcome} | events={events.Count} | LastResultLen={orch.LastResultBufferLength} " +
+            $"| ResultHex={orch.LastResultBufferHex} | ErrHex={orch.LastErrorBufferHex} | Reg=[{orch.RegistrationDiag}]");
     }
 
     [Fact]