Fix Start-Transcript error when $Transcript is a PSObject wrapped string (#24963)

src/Microsoft.PowerShell.ConsoleHost/host/msh/StartTranscriptCmdlet.cs

@@ -177,7 +177,7 @@ namespace Microsoft.PowerShell.Commands
                 }
                 else
                 {
-                    _outFilename = (string)value;
+                    _outFilename = (string)PSObject.Base(value);
                 }
             }
 

test/powershell/Modules/Microsoft.Powershell.Host/Start-Transcript.Tests.ps1

@@ -86,6 +86,11 @@ Describe "Start-Transcript, Stop-Transcript tests" -tags "CI" {
         $outputFilePath = Join-Path $TestDrive "PowerShell_transcript*"
         ValidateTranscription -scriptToExecute $script -outputFilePath $outputFilePath
     }
+    It "Should create Transcript file with 'Transcript' preference variable" {
+        # Casting to PSObject is necessary because Set-Variable does not automatically wrap the value in a PSObject
+        $script = "Set-Variable -Scope Global -Name Transcript -Value ([PSObject]'$transcriptFilePath'); Start-Transcript"
+        ValidateTranscription -scriptToExecute $script -outputFilePath $transcriptFilePath
+    }
     It "Should Append Transcript data in existing file if 'Append' parameter is used with Path parameter" {
         $script = "Start-Transcript -path $transcriptFilePath -Append"
         ValidateTranscription -scriptToExecute $script -outputFilePath $transcriptFilePath -append