Fix prerelease job by specifying download-artifact path

download-artifact@v4 extracts files to the working directory by default,
but the push step expects them under ./nupkg/. Adding path: nupkg fixes the
missing directory error.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Author: anthony-keller

.github/workflows/build.yml

@@ -72,6 +72,7 @@ jobs:
         uses: actions/download-artifact@v4
         with:
           name: nupkg
+          path: nupkg
       - name: Push to GitHub Feed
         run: |
           for f in ./nupkg/*.nupkg