Test enable-fork-prs setting

[danenania]

Testing that enable-fork-prs: true allows fork PR scanning

[promptfoo-scanner-staging]

Code scanning is disabled on fork PRs by default. To scan this PR:

• A maintainer with write permissions can comment on the PR with @promptfoo-scanner-staging to trigger a scan
• Or enable automatic fork scanning in your workflow:

- uses: promptfoo/code-scan-action@v0
  with:
    enable-fork-prs: true