docs: add Signed commits section to CONTRIBUTING

[hyperpolymath]

Adds a Signed commits section to this repo's CONTRIBUTING, per owner ruling D218. The estate policy is docs/SIGNING-POLICY.adoc in hyperpolymath/standards.

This repo's default branch is covered by the zero-bypass Require-Signed-Commits ruleset, and rebase-merge is off. The section tells contributors what that requires:

• People and interactive agents sign with an SSH signing key.
• Apps, bots and workflows write through the API, so GitHub signs their commits.
• PRs are merged with squash.

If the file already had its own signing section, that section is replaced in place instead of adding a second one. Lines elsewhere that told people to sign with GPG are changed to match the policy (SSH for people).

This is a docs-only change. The commit was created through createCommitOnBranch, so GitHub signs it.

🤖 Generated with Claude Code

https://claude.ai/code/session_01WRvDivYwLSeVCJUrfjic3f

[coderabbitai]

Navigate logical layers of code changes, visualize relationships, and explore their blast radius.

No actionable comments were generated in the recent review. 🎉

ℹ️ Recent review info

⚙️ Run configuration

Configuration used: Organization UI

Review profile: ASSERTIVE

Plan: Advanced

Run ID: 721cfddf-e9ae-406d-8eca-ebea3ea5b84d

📥 Commits

Reviewing files that changed from the base of the PR and between fc12a2e and 78f59be.

📒 Files selected for processing (1)

• .github/CONTRIBUTING.md

Included review availability: This review used your included allowance. Your plan provides up to 1 included review per hour; 0 remain after this review.

📜 Recent review details

⏰ Context from checks skipped due to timeout. (21)

• GitHub Check: governance / Check Workflow Staleness
• GitHub Check: governance / Exemption ratchet
• GitHub Check: governance / Debt ratchet
• GitHub Check: governance / Licence consistency
• GitHub Check: governance / Language / package anti-pattern policy
• GitHub Check: governance / Workflow security linter
• GitHub Check: governance / Live Actions policy (credentialed advisory)
• GitHub Check: governance / Actions lockfile verify
• GitHub Check: governance / Well-Known (RFC 9116 + RSR)
• GitHub Check: governance / Trusted-base reduction policy
• GitHub Check: hypatia / Hypatia Neurosymbolic Analysis
• GitHub Check: scan / shell-secrets
• GitHub Check: scan / gitleaks
• GitHub Check: governance / Code quality + docs
• GitHub Check: scan / rust-secrets
• GitHub Check: analyze (actions, none)
• GitHub Check: Validate DEED manifests
• GitHub Check: Groove manifest check
• GitHub Check: Empty-linter (invisible characters)
• GitHub Check: Content placement check
• GitHub Check: semgrep-cloud-platform/scan

🔇 Additional comments (1)

.github/CONTRIBUTING.md (1)

119-134: LGTM!

---

📝 Summary

Summary by CodeRabbit

• Documentation
  • Added contribution guidance requiring signed commits on the default branch, with separate signing instructions for people, interactive agents, apps, bots and workflows.
  • Clarified that unsigned commits block merging and that rebase merges are unavailable.

Walkthrough

The contribution guide adds commit signing requirements for people, interactive agents, apps, bots, and workflows. It also states that unsigned commits block merging and that pull requests must use squash merges.

Changes

Commit signing guidance

Layer / File(s)	Summary
Signing and merge requirements .github/CONTRIBUTING.md	The guide specifies SSH signing and a verified committer email for people and interactive agents. Apps, bots, and workflows use API-based commit creation. Pull requests must be squash-merged; unsigned commits block merging, and rebase-merge is disabled.

Priority: ⬇️ Low

Estimated code review effort: 1 (Trivial) | ~3 minutes

Change: Other

Merge Risk: ⚪ Minimal · up to 78f59

The signing and squash guidance has no demonstrated merge-blocking defect. Whether the external signed-push action reliably produces accepted signatures remains unknown.

Architecture Summary

Architecture risk: 🔵 Low · up to 78f59

The changed surface does not map to a changed system, dependency edge, entrypoint, or external dependency.

Changed systems: None identified.

Architecture concerns
No architecture-level concerns identified.

Review details

Before / after behavior

• observed — Modified behavior in .github/CONTRIBUTING.md: Adds signing requirements and instructions: people and interactive agents sign with a registered SSH signing key and verified committer email; apps, bots and workflows submit commits through the API; and PRs must be squash-merged. Unsigned commits on a PR branch block merging, and rebase-merge is disabled.

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check. Docstring coverage is scoped to functions touched by this diff. Analyzed 0 functions across 0…
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Title check	✅ Passed	The title clearly and concisely describes the documentation change to add a Signed commits section to CONTRIBUTING.
Description check	✅ Passed	The description directly explains the Signed commits documentation change and its policy context.

• Autopilot · Keep fixing CodeRabbit findings and required CI, and resolving merge conflicts

Autopilot is currently an internal CodeRabbit preview.

---

Thanks for using CodeRabbit! It's free for OSS, and your support helps us grow. If you like it, consider giving us a shout-out.

❤️ Share

• X
• Mastodon
• Reddit
• LinkedIn

_{A rabbit signs a commit with care,
SSH keys are ready there.
Verified emails make the mark,
Squash merges guide the work.
Unsigned changes wait outside,
The rabbit hops with signed commits.}

_{Comment @coderabbitai help to get the list of available commands.}

✨ Finishing Touches 💡 1

🛠️ Fix failing CI checks 💡

• Commit to this branch
• Create a new PR