fix(historian): page by the backend's timestamp resolution; QuestDB AtTime stamps the requested time

IHistorianDataSource.TimestampResolutionTicks (default 1; QuestDB 10). A drained tie
cluster now steps off T by the resolution, so a forward one-value-per-page read on a
microsecond backend no longer re-reads the same sample forever (C1). QuestDB AtTime
results carry the client's original request time (M3); regression for the NEXT seek
skipping a tombstone (M1). Conformance backend wires the real writer and updater.

Claude-Session: https://claude.ai/code/session_01Ef2ozxS7QPanGT8uoATbTe

tests/Drivers/ZB.MOM.WW.OtOpcUa.Driver.Historian.QuestDb.IntegrationTests/QuestDbConformance.cs

@@ -0,0 +1,55 @@
+using ZB.MOM.WW.OtOpcUa.Driver.Historian.Conformance;
+using Xunit;
+
+namespace ZB.MOM.WW.OtOpcUa.Driver.Historian.QuestDb.IntegrationTests;
+
+// One concrete subclass per conformance class: the suite's tests run here against QuestDB.
+
+[Collection(QuestDbCollection.Name)]
+public sealed class QuestDbRawReadConformance(QuestDbFixture fx) : RawReadConformance
+{
+    /// <inheritdoc/>
+    protected override Task<IConformanceBackend> CreateBackendAsync() => QuestDbConformanceBackend.CreateAsync(fx);
+}
+
+[Collection(QuestDbCollection.Name)]
+public sealed class QuestDbAtTimeConformance(QuestDbFixture fx) : AtTimeConformance
+{
+    /// <inheritdoc/>
+    protected override Task<IConformanceBackend> CreateBackendAsync() => QuestDbConformanceBackend.CreateAsync(fx);
+}
+
+[Collection(QuestDbCollection.Name)]
+public sealed class QuestDbProcessedConformance(QuestDbFixture fx) : ProcessedConformance
+{
+    /// <inheritdoc/>
+    protected override Task<IConformanceBackend> CreateBackendAsync() => QuestDbConformanceBackend.CreateAsync(fx);
+}
+
+[Collection(QuestDbCollection.Name)]
+public sealed class QuestDbQualityContractConformance(QuestDbFixture fx) : QualityContractConformance
+{
+    /// <inheritdoc/>
+    protected override Task<IConformanceBackend> CreateBackendAsync() => QuestDbConformanceBackend.CreateAsync(fx);
+}
+
+[Collection(QuestDbCollection.Name)]
+public sealed class QuestDbLiveWriteConformance(QuestDbFixture fx) : LiveWriteConformance
+{
+    /// <inheritdoc/>
+    protected override Task<IConformanceBackend> CreateBackendAsync() => QuestDbConformanceBackend.CreateAsync(fx);
+}
+
+[Collection(QuestDbCollection.Name)]
+public sealed class QuestDbUpdateConformance(QuestDbFixture fx) : UpdateConformance
+{
+    /// <inheritdoc/>
+    protected override Task<IConformanceBackend> CreateBackendAsync() => QuestDbConformanceBackend.CreateAsync(fx);
+}
+
+[Collection(QuestDbCollection.Name)]
+public sealed class QuestDbTagNameConformance(QuestDbFixture fx) : TagNameConformance
+{
+    /// <inheritdoc/>
+    protected override Task<IConformanceBackend> CreateBackendAsync() => QuestDbConformanceBackend.CreateAsync(fx);
+}