Copy pyconfig.h into Windows package include

Ensure the generated Windows pyconfig.h (from the PC directory) is present and packaged. The script now checks for the header and throws if missing, then copies it to the package include directory (overwriting if necessary). This guarantees the platform-specific pyconfig.h is bundled for consumers building against the package.

Author: FeodorFitsner

windows/package-for-dart.ps1

@@ -41,6 +41,13 @@ New-Item -ItemType Directory -Force -Path "$packageRoot\DLLs", "$packageRoot\inc
 Copy-Item -Path "$srcDir\Include\*" -Destination "$packageRoot\include" -Recurse -Force
 Copy-Item -Path "$srcDir\Lib\*" -Destination "$packageRoot\Lib" -Recurse -Force
 
+# pyconfig.h is generated/platform-specific and lives under PC on Windows builds.
+$pyconfigHeader = Join-Path $srcDir "PC\pyconfig.h"
+if (-not (Test-Path $pyconfigHeader)) {
+  throw "Missing required header: $pyconfigHeader"
+}
+Copy-Item -Path $pyconfigHeader -Destination "$packageRoot\include\pyconfig.h" -Force
+
 # Root binaries and symbols.
 foreach ($name in @("LICENSE.txt", "NEWS.txt")) {
   $src = Join-Path $srcDir $name