Add test for C#→VB relational pattern conversion (issue #803)

Tests that C# 9 switch statement relational patterns (case < 0:) convert
correctly to VB Case Is < 0 clauses, addressing the missing test noted
in code review.

https://claude.ai/code/session_01AkwUvu3XuCdj3D4axoX4UX

Author: claude

Tests/VB/StatementTests.cs

@@ -1282,6 +1282,34 @@ End Function
 End Class");
     }
 
+    [Fact]
+    public async Task SelectCase_WithRelationalPatternAsync()
+    {
+        await TestConversionCSharpToVisualBasicAsync(@"class TestClass
+{
+    public void Classify(int n)
+    {
+        switch (n) {
+            case < 0:
+                System.Console.Write(""negative"");
+                break;
+            case >= 0:
+                System.Console.Write(""non-negative"");
+                break;
+        }
+    }
+}", @"Friend Class TestClass
+    Public Sub Classify(n As Integer)
+        Select Case n
+            Case Is < 0
+                System.Console.Write(""negative"")
+            Case Is >= 0
+                System.Console.Write(""non-negative"")
+        End Select
+    End Sub
+End Class");
+    }
+
     [Fact]
     public async Task TryCatchAsync()
     {