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/RealTamilNerModelPaths.cs

@@ -0,0 +1,25 @@
+namespace PiiRedaction.Tests.Shared;
+
+public static class RealTamilNerModelPaths
+{
+    public const string ModelMissingMessage =
+        "Tamil ONNX model not found. Run scripts/download-tamil-ner-model.ps1 from the repository root.";
+
+    public static string ResolveRepoModelPath()
+    {
+        const string relativePath = "models/ta/model.onnx";
+        var directory = new DirectoryInfo(AppContext.BaseDirectory);
+        while (directory is not null)
+        {
+            var candidate = Path.Combine(directory.FullName, relativePath);
+            if (File.Exists(candidate))
+            {
+                return candidate;
+            }
+
+            directory = directory.Parent;
+        }
+
+        return Path.Combine(Environment.CurrentDirectory, relativePath);
+    }
+}