Recharacterize switch/select tests and fix TestFileRewriter path for Linux

- Remove blank lines before `default:` and post-switch `return` that
  the converter doesn't actually emit
- Fix TestFileRewriter path separator (backslash → forward slash, add
  missing level) so recharacterization works on Linux

Author: claude

Tests/CSharp/ExpressionTests/ExpressionTests.cs

@@ -2086,7 +2086,6 @@ public void OnLoad(UserInterface? ui)
             case UserInterface.Wisdom:
                 activity = 3;
                 break;
-
             default:
                 activity = 4;
                 break;
@@ -2301,7 +2300,6 @@ public int OnLoad()
                     }
 
                     break;
-
                 default:
                     if (true)
                     {
@@ -2363,7 +2361,6 @@ public void S()
             case var case3 when Operators.ConditionalCompareObjectGreater(case3, 4, false):
                 j = 4;
                 break;
-
             default:
                 j = -1;
                 break;

Tests/CSharp/StatementTests/MethodStatementTests.cs

@@ -1,4 +1,4 @@
-using System.Threading.Tasks;
+using System.Threading.Tasks;
 using ICSharpCode.CodeConverter.Tests.TestRunners;
 using Xunit;
 
@@ -1051,7 +1051,6 @@ private void TestMethod(int number)
             case 5:
                 Console.Write(""section 5"");
                 break;
-
             default:
                 Console.Write(""default section"");
                 break;
@@ -1089,7 +1088,6 @@ public static string TimeAgo(int daysAgo)
                 return ""this week"";
             case > 0:
                 return daysAgo / 7 + "" weeks ago"";
-
             default:
                 return ""in the future"";
         }
@@ -1131,9 +1129,7 @@ public static bool IsPrivileged(UserLevel level)
         switch (level)
         {
             case var @case when (int)UserLevel.City_Staff <= (int)@case && (int)@case <= (int)UserLevel.Fixity_ROOT:
-                {
-                    return true;
-                }
+                return true;
         }
         return false;
     }
@@ -1173,7 +1169,6 @@ public static string TimeAgo(string x)
                 return ""c"";
             case ""d"":
                 return ""d"";
-
             default:
                 return ""e"";
         }
@@ -1226,7 +1221,6 @@ public bool CanDoWork(object Something)
             case object _ when Something is int:
                 // Do something with the Integer
                 return true;
-
             default:
                 // Do something else
                 return false;
@@ -1270,7 +1264,6 @@ public void DoesNotThrow()
                 break;
             case > 4:
                 break;
-
             default:
                 throw new Exception();
         }
@@ -1588,7 +1581,6 @@ private static double d1mach(int i)
             case 2:
                 return double.MaxValue; // the largest magnitude.
         }
-
         return 0d;
     }
 }");
@@ -1623,7 +1615,6 @@ private static string Describe(int i)
             case 2:
                 return ""two"";
         }
-
         return null;
     }
 }");