win: add PowerShell verification in scripts #457

This commit introduces a check at the start of the batch files. It
exists with a clear error message if PowerShell is missing or not in
PATH.

This way, it prevents repeated `'PowerShell' is not recognized'` errors
and provides a more user-friendly failure mode.

src/application/collections/windows.yaml

@@ -9,6 +9,11 @@ scripting:
     startCode: |-
         @echo off
         :: {{ $homepage }} — v{{ $version }} — {{ $date }}
+        :: Ensure PowerShell is available
+        where PowerShell >nul 2>&1 || (
+            echo PowerShell is not available. Please install or enable PowerShell.
+            pause & exit 1
+        )
         :: Ensure admin privileges
         fltmc >nul 2>&1 || (
             echo Administrator privileges are required.