test(c2): env-gated WCF event-read diagnostic spike (RemoteTcpIntegrated)

Drives HistorianWcfEventOrchestrator over RemoteTcpIntegrated and dumps the
native chain (UpdC3/RTag2/EnsT2 return codes, result-buffer length, row count)
to settle whether WCF event reads return rows on an event-bearing 2023 R2 box.
Windows-only, gated by HISTORIAN_WCF_EVENT_HOST, never fails the suite, inert
off Windows. Sanitized: counts + return codes + buffer lengths + sha256 only.

Claude-Session: https://claude.ai/code/session_012SDSQ3AcaXqPcBtDESBRii

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

@@ -0,0 +1,105 @@
+using System.Runtime.Versioning;
+using AVEVA.Historian.Client.Models;
+using AVEVA.Historian.Client.Wcf;
+using Xunit.Abstractions;
+
+namespace AVEVA.Historian.Client.Tests;
+
+/// <remarks>
+/// C2 live diagnostic spike (pending.md C2): does the managed WCF event-read path return rows
+/// against an event-bearing 2023 R2 historian? gRPC event reads are a proven server-side dead-end
+/// (docs/reverse-engineering/grpc-event-query-capture.md); the WCF transport is C2's only listed
+/// unblock but is itself unproven (the orchestrator documents native code 76 / 85 on this server).
+///
+/// Drives <see cref="HistorianWcfEventOrchestrator"/> directly over RemoteTcpIntegrated and dumps the
+/// full native chain. It NEVER fails the suite (skip+log diagnostic) and is inert off Windows — the
+/// GREEN/RED call is by reading the printed "events observed" count + native return codes.
+///
+/// Gated by <c>HISTORIAN_WCF_EVENT_HOST</c> (independent of the gRPC live vars so it never runs by
+/// accident). Optional: <c>HISTORIAN_WCF_EVENT_PORT</c> (default 32568), <c>HISTORIAN_WCF_EVENT_USER</c>
+/// + <c>HISTORIAN_WCF_EVENT_PASSWORD</c> (absent =&gt; IntegratedSecurity), <c>HISTORIAN_WCF_EVENT_SPN</c>
+/// (Kerberos SPN override; the default is the LocalPipe identity and will not authenticate remotely),
+/// <c>HISTORIAN_WCF_EVENT_DAYS</c> (lookback window, default 90 — the live event store held 71,332
+/// events in -90d).
+///
+/// Run from the Windows capture rig over VPN:
+///   dotnet test --filter "FullyQualifiedName~WcfEventReadSpike" -l "console;verbosity=detailed"
+/// </remarks>
+[SupportedOSPlatform("windows")]
+public sealed class WcfEventReadSpikeTests
+{
+    private readonly ITestOutputHelper _output;
+
+    public WcfEventReadSpikeTests(ITestOutputHelper output) => _output = output;
+
+    [Fact]
+    public async Task WcfEventRead_DiagnosticDump_AgainstRemoteHistorian()
+    {
+        string? host = Environment.GetEnvironmentVariable("HISTORIAN_WCF_EVENT_HOST");
+        if (string.IsNullOrWhiteSpace(host) || !OperatingSystem.IsWindows())
+        {
+            return; // inert without the dedicated gate / off Windows
+        }
+
+        int port = int.TryParse(Environment.GetEnvironmentVariable("HISTORIAN_WCF_EVENT_PORT"), out int p)
+            ? p : HistorianClientOptions.DefaultPort; // 32568
+        int days = int.TryParse(Environment.GetEnvironmentVariable("HISTORIAN_WCF_EVENT_DAYS"), out int d)
+            ? d : 90;
+        string? user = Environment.GetEnvironmentVariable("HISTORIAN_WCF_EVENT_USER");
+        string? password = Environment.GetEnvironmentVariable("HISTORIAN_WCF_EVENT_PASSWORD");
+        string? spn = Environment.GetEnvironmentVariable("HISTORIAN_WCF_EVENT_SPN");
+        bool integrated = string.IsNullOrEmpty(user);
+
+        HistorianClientOptions options = new()
+        {
+            Host = host,
+            Port = port,
+            Transport = HistorianTransport.RemoteTcpIntegrated,
+            IntegratedSecurity = integrated,
+            UserName = user ?? string.Empty,
+            Password = password ?? string.Empty,
+            TargetSpn = string.IsNullOrWhiteSpace(spn) ? "NT SERVICE\\aahClientAccessPoint" : spn,
+        };
+
+        HistorianWcfEventOrchestrator orchestrator = new(options);
+        DateTime endUtc = DateTime.UtcNow;
+        DateTime startUtc = endUtc - TimeSpan.FromDays(days);
+
+        int observed = 0;
+        bool hasFirstEvent = false;
+        string outcome = "completed";
+        try
+        {
+            await foreach (HistorianEvent evt in orchestrator.ReadEventsAsync(startUtc, endUtc, filter: null, CancellationToken.None))
+            {
+                observed++;
+                hasFirstEvent = true;
+                _ = evt; // event identity intentionally NOT logged (sanitized)
+            }
+        }
+        catch (Exception ex)
+        {
+            outcome = $"threw {ex.GetType().Name}"; // message omitted — may carry host/credential text
+        }
+
+        // Sanitized diagnostic dump — counts, native return codes, buffer lengths, sha256 ONLY.
+        _output.WriteLine($"[C2 WCF spike] outcome:                  {outcome}");
+        _output.WriteLine($"[C2 WCF spike] events observed:          {observed}");
+        _output.WriteLine($"[C2 WCF spike] hasFirstEvent:            {hasFirstEvent}");
+        _output.WriteLine($"[C2 WCF spike] LastUpdC3ReturnCode:      {HistorianWcfEventOrchestrator.LastUpdC3ReturnCode}");
+        _output.WriteLine($"[C2 WCF spike] LastRTag2ReturnCode:      {HistorianWcfEventOrchestrator.LastRTag2ReturnCode}");
+        _output.WriteLine($"[C2 WCF spike] LastAddReturnCode(EnsT2): {HistorianWcfEventOrchestrator.LastAddReturnCode}");
+        _output.WriteLine($"[C2 WCF spike] LastAddOutputLength:      {HistorianWcfEventOrchestrator.LastAddOutputLength}");
+        _output.WriteLine($"[C2 WCF spike] LastEnsT2PayloadSha256:   {HistorianWcfEventOrchestrator.LastEnsT2PayloadSha256}");
+        _output.WriteLine($"[C2 WCF spike] LastResultBufferLength:   {orchestrator.LastResultBufferLength}");
+        // Contract-safe: LastErrorBufferDescription is DescribeNativeError's STRUCTURED formatting of the
+        // 5-byte native error buffer ("type=N code=M (0xHEX)" / "<short>") — never freeform server text,
+        // FQDN, SPN, or credentials. The code value (e.g. 76 / 85) is the RED-case signal this spike exists
+        // to capture, so it is dumped in full rather than reduced to a length.
+        _output.WriteLine($"[C2 WCF spike] LastErrorBufferDescription: {orchestrator.LastErrorBufferDescription}");
+        _output.WriteLine($"[C2 WCF spike] window days:              {days}");
+
+        // Diagnostic: NEVER fails the suite. GREEN = observed > 0; RED = observed == 0 (read the output).
+        Assert.True(observed >= 0, "diagnostic always passes; the GREEN/RED signal is the printed count");
+    }
+}