feat: complete legacy parity and modernize operator UI

tests/MBN_STOCK_WEBVIEW.LegacyWeb.Tests/LegacyInteractionMetricsNativeContractTests.cs

@@ -34,6 +34,15 @@ public sealed class LegacyInteractionMetricsNativeContractTests
         Assert.DoesNotContain("GetSystemMetrics(", Window, StringComparison.Ordinal);
         Assert.Contains("LegacyInteractionMetrics.FromPixelsAtDpi(", Window,
             StringComparison.Ordinal);
+        Assert.Contains("private static extern uint GetDoubleClickTime();", Window,
+            StringComparison.Ordinal);
+        Assert.Contains(
+            "doubleClickTimeMilliseconds: (int)GetDoubleClickTime()",
+            Window,
+            StringComparison.Ordinal);
+        Assert.Equal(2, CountOccurrences(
+            Window,
+            "[DllImport(\"user32.dll\", ExactSpelling = true)]"));
         Assert.Contains("logical DIP coordinate space used by XAML", Window,
             StringComparison.Ordinal);
         Assert.Contains("Root.XamlRoot?.RasterizationScale", Window,