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: ec3dde77-22b5-4f4c-b393-e73479b9258d

📥 Commits

Reviewing files that changed from the base of the PR and between f592e02 and 569b0f0.

📒 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. (19)

• GitHub Check: semgrep-cloud-platform/scan
• GitHub Check: scan / gitleaks
• GitHub Check: scan / shell-secrets
• GitHub Check: scan / rust-secrets
• GitHub Check: hypatia / Hypatia Neurosymbolic Analysis
• GitHub Check: governance / Guix primary / Nix fallback policy
• GitHub Check: governance / Well-Known (RFC 9116 + RSR)
• GitHub Check: governance / Check Workflow Staleness
• GitHub Check: governance / Workflow security linter
• GitHub Check: governance / Language / package anti-pattern policy
• GitHub Check: governance / Security policy checks
• GitHub Check: governance / Trusted-base reduction policy
• GitHub Check: governance / Licence consistency
• GitHub Check: governance / Code quality + docs
• GitHub Check: Empty-linter (invisible characters)
• GitHub Check: analyze (javascript-typescript, none)
• GitHub Check: Validate K9 contracts
• GitHub Check: Groove manifest check
• GitHub Check: Validate DEED manifests

🔇 Additional comments (1)

.github/CONTRIBUTING.md (1)

90-105: LGTM!

---

📝 Summary

Summary by CodeRabbit

• Documentation
  • Added guidance on commit-signing requirements and supported commit methods for people, agents, apps, and workflows.
  • Clarified how unsigned commits affect pull requests and which merge methods are available.

Walkthrough

The contribution guide now explains signed-commit requirements for people, interactive agents, apps, bots and workflows. It also documents squash merging, disabled rebase merging, and steps for pull requests blocked by unsigned commits.

Changes

Signed commit guidance

Layer / File(s)	Summary
Document signing and merge requirements .github/CONTRIBUTING.md	Adds signing instructions for people and interactive agents, API-based commit creation guidance for apps, bots and workflows, and pull request merge requirements.

Priority: ⬇️ Low

Estimated code review effort: 1 (Trivial) | ~4 minutes

Change: Other

Suggested reviewers: metadatastician

Merge Risk: ⚪ Minimal · up to 569b0

Unsigned commits can block pull requests, making the core signing guidance consistent with GitHub behavior. The repository's squash/rebase setting remains unclear, but no established issue warrants delaying this docs-only change.

Architecture Summary

Architecture risk: 🔵 Low · up to 569b0

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: Added signed-commit guidance: people and interactive agents use a registered GitHub SSH signing key and verified committer email; apps, bots and workflows write commits through the API rather than pushing local commits. It also states that PRs must be squash-merged because the ruleset checks every branch commit, and prescribes recreating branches with signed commits when unsigned commits block merging; rebase-merge is disabled.

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title clearly and concisely describes the main change: adding a Signed commits section to CONTRIBUTING.
Description check	✅ Passed	The description directly explains the documentation change and its signing-policy context.
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.

• 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 beneath the moon
Then checks each commit, neat and soon
Squash the branch and close the gate
No unsigned hops will pass the state
The guide now shows the way ahead}

_{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