fix: MockFileSystem.GetTempPath() now returns real OS temp path by default

Replace the hardcoded C:\temp\ constant (converted via XFS.Path) with
System.IO.Path.GetTempPath() so the default mirrors the actual environment.
Callers can still override by passing an explicit temp directory.

Co-Authored-By: Claude Sonnet 4.6 (1M context) <noreply@anthropic.com>

Author: Mpdreamz

src/TestableIO.System.IO.Abstractions.TestingHelpers/MockFileSystem.cs

@@ -14,7 +14,6 @@ namespace System.IO.Abstractions.TestingHelpers;
 public class MockFileSystem : FileSystemBase, IMockFileDataAccessor
 {
     private const string DEFAULT_CURRENT_DIRECTORY = @"C:\";
-    private const string TEMP_DIRECTORY = @"C:\temp\";
 
     private readonly IDictionary<string, FileSystemEntry> files;
     private readonly IDictionary<string, MockDriveData> drives;
@@ -58,7 +57,7 @@ public MockFileSystem(IDictionary<string, MockFileData> files, MockFileSystemOpt
             throw new ArgumentException("Current directory needs to be rooted.", nameof(currentDirectory));
         }
 
-        var defaultTempDirectory = XFS.Path(TEMP_DIRECTORY);
+        var defaultTempDirectory = System.IO.Path.GetTempPath();
 
         StringOperations = new StringOperations(XFS.IsUnixPlatform());
         pathVerifier = new PathVerifier(this);

tests/TestableIO.System.IO.Abstractions.TestingHelpers.Tests/MockPathTests.cs

@@ -412,6 +412,19 @@ public async Task GetTempPath_Called_ReturnsStringLengthGreaterThanZero(string t
         await That(result.Length > 0).IsTrue();
     }
 
+    [Test]
+    public async Task GetTempPath_Default_MatchesRealOsTempPath()
+    {
+        //Arrange
+        var mockPath = new MockFileSystem().Path;
+
+        //Act
+        var result = mockPath.GetTempPath();
+
+        //Assert
+        await That(result).IsEqualTo(System.IO.Path.GetTempPath());
+    }
+
     [Test]
     public async Task GetTempPath_Called_WithNonNullVirtualTempDirectory_ReturnsVirtualTempDirectory()
     {