test: docs/serverless backport workflow research (authorized, will self-close)

[juanzahi]

Authorized bug-bounty CI/CD workflow research (HackerOne Elastic program, Software Supply Chain scope). Testing GitHub Actions script-injection reachability via branch-name interpolation in delete-serverless-dir-in-backports.yml. No malicious payload - injected command is a benign echo of a marker string for verification only. Will close this PR immediately after collecting evidence. Apologies for the noise.

[github-actions]

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[cla-checker-service]

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[mergify]

This pull request is now in conflicts. Could you fix it @juanzahi? 🙏
To fixup this pull request, you can check out it locally. See documentation: https://help.github.com/articles/checking-out-pull-requests-locally/

git fetch upstream
git checkout -b 8.5-test$(echo${IFS}BBPOC_0cb3b8dab645) upstream/8.5-test$(echo${IFS}BBPOC_0cb3b8dab645)
git merge upstream/8.5
git push upstream 8.5-test$(echo${IFS}BBPOC_0cb3b8dab645)

[juanzahi]

Testing complete, closing per plan. Thanks for your patience.