The GITHUB_TOKEN for fork PRs is read-only — gh pr comment fails with
'Resource not accessible by integration'. This caused the supply chain
scan to show a red X on every fork PR even when no findings were detected.
The scan itself still runs and the 'Fail on critical findings' step
still exits 1 on real issues. Only the comment posting is gracefully
skipped for fork PRs.
Closes#6679
Co-authored-by: SHL0MS <SHL0MS@users.noreply.github.com>