chore(policy): pre-register fixture digest for #2905 test cleanup - #2917

On November 2, 2026, GitHub will restrict `pull_request_target` on public repositories by default. To continue allowing the event trigger, configure an Actions policy. Learn more: https://gh.io/securely-using-pull_request_target#default-policy-for-pull_request_target

No file matched to [/home/runner/work/benchbox/benchbox/**/*requirements*.txt,/home/runner/work/benchbox/benchbox/**/*requirements*.in,/home/runner/work/benchbox/benchbox/**/*constraints*.txt,/home/runner/work/benchbox/benchbox/**/*constraints*.in,/home/runner/work/benchbox/benchbox/**/pyproject.toml,/home/runner/work/benchbox/benchbox/**/uv.lock,/home/runner/work/benchbox/benchbox/**/*.py.lock]. The cache will never get invalidated. Make sure you have checked out the target repository and configured the cache-dependency-glob input correctly.