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/TestSupport.Shared/RealRoutingNerModelFixture.cs

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+using Microsoft.Extensions.Logging.Abstractions;
+using Microsoft.Extensions.Options;
+using PiiRedaction.Core.Configuration;
+using PiiRedaction.Infrastructure.Onnx;
+
+namespace PiiRedaction.Tests.Shared;
+
+/// <summary>
+/// Loads English and Tamil ONNX runners and exposes a <see cref="RoutingOnnxNerModelRunner"/>.
+/// Skips when either model is missing or cannot be loaded.
+/// </summary>
+public abstract class RealRoutingNerModelFixture
+{
+    protected RoutingOnnxNerModelRunner Runner { get; private set; } = null!;
+
+    protected EnglishOnnxNerRunner EnglishRunner { get; private set; } = null!;
+
+    protected TamilOnnxNerRunner TamilRunner { get; private set; } = null!;
+
+    [OneTimeSetUp]
+    public void OneTimeSetUpRoutingModels()
+    {
+        var englishPath = RealNerModelPaths.ResolveRepoModelPath();
+        if (!File.Exists(englishPath))
+        {
+            Assert.Ignore(RealNerModelPaths.ModelMissingMessage);
+        }
+
+        var tamilPath = RealTamilNerModelPaths.ResolveRepoModelPath();
+        if (!File.Exists(tamilPath))
+        {
+            Assert.Ignore(RealTamilNerModelPaths.ModelMissingMessage);
+        }
+
+        var options = Options.Create(new PiiRedactionOptions
+        {
+            EnglishOnnxModelPath = englishPath,
+            OnnxModelPath = englishPath,
+            TamilOnnxModelPath = tamilPath,
+            EnableTamilNer = true
+        });
+
+        EnglishRunner = new EnglishOnnxNerRunner(options, NullLogger<EnglishOnnxNerRunner>.Instance);
+        TamilRunner = new TamilOnnxNerRunner(options, NullLogger<TamilOnnxNerRunner>.Instance);
+
+        if (!EnglishRunner.IsModelAvailable)
+        {
+            EnglishRunner.Dispose();
+            TamilRunner.Dispose();
+            Assert.Ignore(RealNerModelPaths.ModelMissingMessage);
+        }
+
+        if (!TamilRunner.IsModelAvailable)
+        {
+            EnglishRunner.Dispose();
+            TamilRunner.Dispose();
+            Assert.Ignore(RealTamilNerModelPaths.ModelMissingMessage);
+        }
+
+        Runner = new RoutingOnnxNerModelRunner(EnglishRunner, TamilRunner, options);
+    }
+
+    [OneTimeTearDown]
+    public void OneTimeTearDownRoutingModels()
+    {
+        EnglishRunner?.Dispose();
+        TamilRunner?.Dispose();
+    }
+}