[jserv]

Problem and behavior

The interactive-review check could not tell whether a contributor ran the
interactive review. It waited for the explained label, and on fork pull
requests it failed outright (run 42251304697). Only the pre-push hook enforced
the review, so a contributor without the hooks, or pushing past them, reached a
green check.

After this change, the pre-push hook signs a review record on the author's
machine and pushes it with the branch as the git note
refs/notes/codetrial-review. The signature covers a fingerprint of the
project, head, base, diff hash and answer digest; the note carries none of the
answers. The check measures the diff. Below the thresholds it passes. Above
them it verifies the record against the author's public SSH keys on GitHub. The
PR description and labels play no part.

Exemptions:

• a pull request whose opener and every commit author are in the base branch's
  CODEOWNERS;
• Dependabot;
• the maintainer's ruleset bypass.

Every failure names its fix:

• a missing key prints the three setup steps;
• a key outage asks for a retry, not new setup;
• a branch that is already pushed can send its record alone with
  sh scripts/git-pre-push.sh --publish-review <fork-remote> [<branch>].

Approach

• The check stays on pull_request_target, so a pull request cannot edit the
  check that judges it.
• The checker runs from the base branch against a bare fetch of the head; no
  file from the pull request is on disk.
• GitHub restricts that trigger from 2026-12-02, so an Actions event policy
  scoped to pr-description.yml now allows it (created as id 11911).
• docs/large-change-explanation.md owns the rules and every recovery path.
  CONTRIBUTING and the skills link to it.
• The approver's "explain one passage" rule is withdrawn until it can be
  enforced; a FIXME in docs/development.md and one in the checker track it.
• A merge group passes at once: the queue takes a pull request only after this
  check passed on its own head (the ruleset requires it).
• check-queue-review.py drops its --guard, --branch and --repo options,
  which nothing calls any more.
• The check also reruns when a pull request is edited, so a pull request moved
  to another base is measured again. The token is unset before anything reads
  the pull request's data.

Validation

• scripts/run-python-tests.py on the review-hook and hashchain tests: 104
  pass. Mutations of the base-ancestor check, the commit-list match, the
  push-URL lookup and the record restore after the notes merge each fail a
  test.
• ./scripts/test.sh portable: passes except test-gate-tests, which needs
  cryptography in the local Python and does not touch this change.
• scripts/check-skill-refs.py: passes.
• scripts/hashchain.py verify: passes.
• make indent: clean.
• actionlint and shellcheck on the workflow: pass.
• Merges cleanly with Show what a force push changed since a review #605; the tests on the merged tree pass.

Not checked: a real notes push and signature check from a fork pull request. A
contributor's next large-change run after merge is the first live test.