Close scratch iteration 007 and harden runner output contracts

scripts/run-clean-scratch-iterations.ps1

@@ -31,9 +31,21 @@ function Invoke-External {
 
     Push-Location $WorkingDirectory
     try {
-        & $FilePath @ArgumentList
+        $resolvedFilePath = $FilePath
+        if (Test-Path $FilePath) {
+            $resolvedFilePath = (Resolve-Path $FilePath).Path
+        }
+
+        if ([System.IO.Path]::GetExtension($resolvedFilePath).Equals('.ps1', [System.StringComparison]::OrdinalIgnoreCase)) {
+            $powershellPath = (Get-Command powershell.exe -ErrorAction Stop).Source
+            & $powershellPath -NoLogo -NoProfile -ExecutionPolicy Bypass -File $resolvedFilePath @ArgumentList 2>&1 | Out-Host
+        }
+        else {
+            & $resolvedFilePath @ArgumentList 2>&1 | Out-Host
+        }
+
         if ($LASTEXITCODE -ne 0) {
-            throw "Command failed: $FilePath $($ArgumentList -join ' ')"
+            throw "Command failed: $resolvedFilePath $($ArgumentList -join ' ')"
         }
     }
     finally {