Add PII redaction POC for secure LLM prompting.

Implements detect-redact-sanitize pipeline with regex, domain rules, and ONNX NER before the LLM boundary, plus NUnit tests and Xenovex push documentation.

Co-authored-by: Cursor <cursoragent@cursor.com>

tests/PiiRedaction.Infrastructure.Tests/Onnx/OnnxNerModelRunnerTests.cs

@@ -0,0 +1,53 @@
+using FluentAssertions;
+using Microsoft.Extensions.Logging.Abstractions;
+using Microsoft.Extensions.Options;
+using PiiRedaction.Core.Configuration;
+using PiiRedaction.Core.Models;
+using PiiRedaction.Infrastructure.Onnx;
+
+namespace PiiRedaction.Infrastructure.Tests.Onnx;
+
+[TestFixture]
+public sealed class OnnxNerModelRunnerTests
+{
+    [Test]
+    public void Constructor_MissingModel_IsModelUnavailable()
+    {
+        var path = Path.Combine(Path.GetTempPath(), $"missing-ner-{Guid.NewGuid():N}.onnx");
+        using var runner = CreateRunner(path);
+
+        runner.IsModelAvailable.Should().BeFalse();
+    }
+
+    [Test]
+    public void PredictEntities_WhenModelUnavailable_ReturnsEmpty()
+    {
+        var path = Path.Combine(Path.GetTempPath(), $"missing-ner-{Guid.NewGuid():N}.onnx");
+        using var runner = CreateRunner(path);
+
+        runner.PredictEntities("Customer Ravi Kumar").Should().BeEmpty();
+    }
+
+    [Test]
+    public void Constructor_InvalidModelFile_IsModelUnavailable()
+    {
+        var path = Path.Combine(Path.GetTempPath(), $"invalid-ner-{Guid.NewGuid():N}.onnx");
+        File.WriteAllText(path, "not-a-valid-onnx-model");
+
+        try
+        {
+            using var runner = CreateRunner(path);
+            runner.IsModelAvailable.Should().BeFalse();
+        }
+        finally
+        {
+            File.Delete(path);
+        }
+    }
+
+    private static OnnxNerModelRunner CreateRunner(string modelPath)
+    {
+        var options = Options.Create(new PiiRedactionOptions { OnnxModelPath = modelPath });
+        return new OnnxNerModelRunner(options, NullLogger<OnnxNerModelRunner>.Instance);
+    }
+}

tests/PiiRedaction.Infrastructure.Tests/Onnx/RealNerModelRunnerTests.cs

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+using FluentAssertions;
+
+using PiiRedaction.Core.Models;
+
+using PiiRedaction.Tests.Shared;
+
+
+
+namespace PiiRedaction.Infrastructure.Tests.Onnx;
+
+
+
+[TestFixture]
+
+[Category("RealModel")]
+
+public sealed class RealNerModelRunnerTests : RealNerModelFixture
+
+{
+
+    [TestCase("Customer Ravi Kumar called about billing.", "Ravi", "Ravi Kumar")]
+
+    [TestCase("Mr. John Smith called about a duplicate debit.", "John", "John Smith")]
+
+    public void PredictEntities_DetectsPersonWithCorrectSpan(string prompt, string expectedNamePart, string expectedValue)
+
+    {
+
+        var entities = Runner.PredictEntities(prompt);
+
+
+
+        entities.Should().Contain(entity =>
+
+            entity.Type == PiiEntityType.Person &&
+
+            entity.Source == PiiDetectionSource.Ner &&
+
+            entity.Value.Contains(expectedNamePart, StringComparison.Ordinal) &&
+
+            prompt.AsSpan(entity.StartIndex, entity.Length).ToString() == entity.Value);
+
+
+
+        entities.Should().Contain(entity => entity.Value == expectedValue);
+
+    }
+
+}
+
+