R1.7: server-side event filters — ReadEventsAsync(HistorianEventFilter), live-honored

Roadmap M1 R1.7. Filters are set on the native EventQuery object via
AddEventFilter(property, HistorianComparisionType, value) — NOT EventQueryArgs
(time/count/order only). Found via a new harness --dump-type-members command.

Captured the native filtered StartEventQuery pRequestBuff (Capture-EventFilter.ps1 +
harness --event-filter knob) and diffed Equal(0) vs Contains(12) to isolate the
operator field. Filter block (decoded byte-for-byte):
  ushort 0 + uint filterCount + uint condCount + uint nameLen + name(UTF-16) +
  uint 1 + ushort op + uint 1 + value(0x09-LEN-0x00 compact-ASCII) + byte 0

The filter is REAL, not inert (unlike the analog-summary knobs): a non-matching
predicate returns 0 events; Type=Equal=User.Write returns only User.Write events.
Verified live via both the native harness and the SDK.

- HistorianClient.ReadEventsAsync(start, end, HistorianEventFilter, ct) overload
- HistorianEventFilter + HistorianEventComparison (18 ops, ordinals = native)
- Filter encoding in HistorianEventQueryProtocol (empty-filter path unchanged)
- Golden-byte tests (block match, op field, empty-filter regression) + gated live test

Single string-valued predicate only; multi-filter (OR) / multi-condition (AND via
AddEventFilterCondition) framing is partially captured and not shipped. 216 unit
tests pass.

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/WcfEventQueryProtocolTests.cs

@@ -1,9 +1,63 @@
+using AVEVA.Historian.Client.Models;
 using AVEVA.Historian.Client.Wcf;
 
 namespace AVEVA.Historian.Client.Tests;
 
 public sealed class WcfEventQueryProtocolTests
 {
+    // Filter block (offset 0x1E into pRequestBuff) captured from a native
+    // EventQuery.AddEventFilter("Area", Equal, "RetestFilterArea") StartEventQuery, via
+    // instrument-wcf-writemessage.
+    private const string CaptureFilterBlockHex =
+        "000001000000010000000400000041007200650061000100000000000100000009100052657465737446696c7465724172656100";
+    private const int FilterBlockOffset = 0x1E;
+
+    [Fact]
+    public void SerializerMatchesInstrumentedNativeEventFilterBlock()
+    {
+        HistorianEventQueryAttempt attempt = Assert.Single(HistorianEventQueryProtocol.CreateStartEventQueryAttempts(
+            new DateTime(2026, 1, 1, 0, 0, 0, DateTimeKind.Utc),
+            new DateTime(2026, 1, 2, 0, 0, 0, DateTimeKind.Utc),
+            5,
+            new HistorianEventFilter("Area", HistorianEventComparison.Equal, "RetestFilterArea")));
+
+        byte[] expectedBlock = Convert.FromHexString(CaptureFilterBlockHex);
+        byte[] actualBlock = attempt.RequestBuffer[FilterBlockOffset..(FilterBlockOffset + expectedBlock.Length)];
+
+        Assert.Equal("native-filter-version5", attempt.Name);
+        Assert.Equal(expectedBlock, actualBlock);
+    }
+
+    [Fact]
+    public void FilterBlockEncodesComparisonOperatorAsUInt16()
+    {
+        // Equal = 0, Contains = 12 — the op field is the only byte that differs between them
+        // (offset 0x38 in pRequestBuff = 0x1A into the filter block).
+        byte[] equal = HistorianEventQueryProtocol.CreateStartEventQueryAttempts(
+            new DateTime(2026, 1, 1, 0, 0, 0, DateTimeKind.Utc),
+            new DateTime(2026, 1, 2, 0, 0, 0, DateTimeKind.Utc),
+            5, new HistorianEventFilter("Area", HistorianEventComparison.Equal, "X"))[0].RequestBuffer;
+        byte[] contains = HistorianEventQueryProtocol.CreateStartEventQueryAttempts(
+            new DateTime(2026, 1, 1, 0, 0, 0, DateTimeKind.Utc),
+            new DateTime(2026, 1, 2, 0, 0, 0, DateTimeKind.Utc),
+            5, new HistorianEventFilter("Area", HistorianEventComparison.Contains, "X"))[0].RequestBuffer;
+
+        Assert.Equal(0x38, FilterBlockOffset + 0x1A);
+        Assert.Equal(0, BitConverter.ToUInt16(equal, 0x38));
+        Assert.Equal(12, BitConverter.ToUInt16(contains, 0x38));
+    }
+
+    [Fact]
+    public void NullFilterStillProducesTheEmptyFilterBuffer()
+    {
+        HistorianEventQueryAttempt withNull = HistorianEventQueryProtocol.CreateStartEventQueryAttempts(
+            new DateTime(2026, 1, 1, 0, 0, 0, DateTimeKind.Utc),
+            new DateTime(2026, 1, 1, 0, 1, 0, DateTimeKind.Utc), 3)[0];
+
+        Assert.Equal("native-empty-filter-version5", withNull.Name);
+        Assert.Equal(65, withNull.RequestBuffer.Length);
+    }
+
     [Fact]
     public void SerializerMatchesInstrumentedNativeEventRequest()
     {