Summary

• Normalize APPCAST_DOWNLOAD_URL_PREFIX to include a trailing slash before passing it to Sparkle.
• Keep the combined release asset script's default prefix as the concrete release tag directory URL.
• Document the trailing-slash normalization for future releases.

Verification

• bash -n scripts/generate-appcast.sh scripts/create-release-assets.sh
• APPCAST_DOWNLOAD_URL_PREFIX="https://github.com/jx-grxf/SlamX/releases/download/v0.3.2" ./scripts/generate-appcast.sh .build/dmg
• swift test