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.Core.Tests/Detection/ScriptRouterTests.cs

@@ -0,0 +1,54 @@
+using FluentAssertions;
+using PiiRedaction.Core.Detection;
+using PiiRedaction.Infrastructure.Onnx;
+
+namespace PiiRedaction.Core.Tests.Detection;
+
+[TestFixture]
+public sealed class ScriptRouterTests
+{
+    private readonly ScriptRouter _router = new();
+
+    [Test]
+    public void GetComposition_LatinOnly_ReturnsLatinOnly()
+    {
+        _router.GetComposition("Customer Ravi Kumar called about billing.")
+            .Should().Be(ScriptComposition.LatinOnly);
+    }
+
+    [Test]
+    public void GetComposition_TamilOnly_ReturnsTamilOnly()
+    {
+        _router.GetComposition("வாடிக்கையாளர் ராஜேஷ் தொலைபேசி 9876543210")
+            .Should().Be(ScriptComposition.TamilOnly);
+    }
+
+    [Test]
+    public void GetComposition_Mixed_ReturnsMixed()
+    {
+        _router.GetComposition("Rajesh மற்றும் Priya disputed the charge.")
+            .Should().Be(ScriptComposition.Mixed);
+    }
+
+    [Test]
+    public void GetComposition_MixedTamilEnglishSample_ReturnsMixed()
+    {
+        _router.GetComposition("வாடிக்கையாளர் Ravi Kumar phone 9876543210 disputed the charge.")
+            .Should().Be(ScriptComposition.Mixed);
+    }
+
+    [Test]
+    public void GetComposition_NoLetters_ReturnsNoLetters()
+    {
+        _router.GetComposition("9876543210 12345")
+            .Should().Be(ScriptComposition.NoLetters);
+    }
+
+    [Test]
+    public void GetComposition_TamilBoundaryChars_AreClassifiedAsTamil()
+    {
+        _router.GetComposition("\u0B80").Should().Be(ScriptComposition.TamilOnly);
+        _router.GetComposition("\u0BFF").Should().Be(ScriptComposition.TamilOnly);
+        _router.GetComposition("A").Should().Be(ScriptComposition.LatinOnly);
+    }
+}