Forgejo Actions runs in GHES compat mode and the bundled @actions/artifact toolkit only supports the v3 protocol. v4 fails with:
GHESNotSupportedError: @actions/artifact v2.0.0+, upload-artifact@v4+ and download-artifact@v4+ are not currently supported on GHES.
Build, tests (72/72), and the 80% coverage gate (currently 86.7%) all pass; only the trailing artifact-upload steps were red, which fails the whole run. Pinning to v3 restores green.
