Add Tamil NER routing and WPF test harness for POC validation.

Introduce dual-script ONNX NER routing (English/Tamil/mixed), Tamil console samples and integration tests, model download scripts, and a resizable WPF MVVM harness with click-to-load prompts, batch validation, and runtime-adjustable detection panels.

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

@@ -0,0 +1,43 @@
+using FluentAssertions;
+using Microsoft.Extensions.Logging.Abstractions;
+using PiiRedaction.Infrastructure.Onnx;
+
+namespace PiiRedaction.Infrastructure.Tests.Onnx;
+
+[TestFixture]
+public sealed class TokenClassifierEncoderFactoryTests
+{
+    [Test]
+    public void Create_PrefersWordPieceWhenVocabExists()
+    {
+        var modelDirectory = ResolveTamilModelDirectory();
+        if (!File.Exists(Path.Combine(modelDirectory, "vocab.txt")))
+        {
+            Assert.Ignore("Tamil vocab.txt not found.");
+        }
+
+        var encoder = TokenClassifierEncoderFactory.Create(
+            modelDirectory,
+            NullLogger.Instance);
+
+        encoder.Should().BeOfType<BertWordPieceEncoder>();
+        encoder.IsAvailable.Should().BeTrue();
+    }
+
+    private static string ResolveTamilModelDirectory()
+    {
+        var directory = new DirectoryInfo(AppContext.BaseDirectory);
+        while (directory is not null)
+        {
+            var candidate = Path.Combine(directory.FullName, "models", "ta");
+            if (Directory.Exists(candidate))
+            {
+                return candidate;
+            }
+
+            directory = directory.Parent;
+        }
+
+        return Path.Combine(Environment.CurrentDirectory, "models", "ta");
+    }
+}