chore: fix 'windows' pull request check; head_ref is the branch name …

…while ref ends up being a generated GH actions branch name for the PR

.github/workflows/ci.yaml

@@ -63,7 +63,7 @@ jobs:
         run: echo "os=windows-latest" >> $GITHUB_OUTPUT
         # Only run on main branch (or PR branches that contain 'windows') to minimize Windows minutes (billed at 2X)
         # https://docs.github.com/en/billing/managing-billing-for-github-actions/about-billing-for-github-actions#included-storage-and-minutes
-        if: ${{ github.ref == 'refs/heads/main' || contains(github.ref, 'windows') }}
+        if: ${{ github.ref == 'refs/heads/main' || contains(github.head_ref, 'windows') }}
     outputs:
       # Will look like ["ubuntu-latest", "macos-latest", "windows-latest"]
       os: ${{ toJSON(steps.*.outputs.os) }}