benchmark-pr: a --save run whose results push is refused (org fork) still reports success #1702

What happens. When the head of a PR is an organization fork, GitHub does not allow "Allow edits by maintainers", so the results commit that /benchmark --save makes cannot be pushed back. The "Commit saved results" step in .github/workflows/benchmark-pr.yml does:

git push origin HEAD:"${PR_BRANCH}" || echo "Warning: could not push to fork (permissions)"

The push fails with 403, the step prints the warning, the job ends green, and the PR comment looks the same as a saved run. Nothing on the PR says the results were not saved, so the PR can be merged without them.

Example. #1668 (mipyre, head leocaolab/HttpArena). Run 40687985062:

[detached HEAD a28d9e6a7] Benchmark results: mipyre  [skip ci]
remote: Permission to leocaolab/HttpArena.git denied to github-actions[bot].
fatal: unable to access 'https://github.com/leocaolab/HttpArena.git/': The requested URL returned error: 403
Warning: could not push to fork (permissions)

The run is marked success. #1668 was merged on 2026-10-31 with frameworks/mipyre/ but no site/data/results/mipyre.json.

Suggestion. When the push fails on a --save run, say so in the PR comment (for example "⚠️ results not saved: could not push to <fork> (403). Enable Allow edits by maintainers, or the maintainer can run the Benchmark workflow with save=true after merge") and mark the job failed, the same way the job is already flagged red when a framework's benchmark fails. Optionally, check maintainerCanModify before running a --save benchmark and refuse early, so the machine time is not spent on results that cannot be saved.