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: 650e7c91-9215-45b5-ae5c-d7d0841e0a01

📥 Commits

Reviewing files that changed from the base of the PR and between ed3e94f and f4032cf.

📒 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. (7)

• GitHub Check: semgrep-cloud-platform/scan
• GitHub Check: secret-scan / gitleaks
• GitHub Check: secret-scan / rust-secrets
• GitHub Check: call-estate-audit / estate-audit
• GitHub Check: CodeQL Analysis (actions)
• GitHub Check: CodeQL Analysis (rust)
• GitHub Check: check

🔇 Additional comments (1)

.github/CONTRIBUTING.md (1)

123-138: LGTM!

---

📝 Summary

Summary by CodeRabbit

• Documentation
  • Added guidance on signing commits, handling unsigned commits on pull requests, and using squash merges. Rebase merges are disabled.

Walkthrough

The contribution guide adds instructions for signing commits, handling unsigned commits on pull request branches, and using squash merges.

Changes

Signed commit guidance

Layer / File(s)	Summary
Commit signing and merge instructions .github/CONTRIBUTING.md	The guide explains signing requirements for people, interactive agents, apps, bots and workflows. It describes how to handle unsigned commits on pull request branches and states that squash merges are required because rebase merges are disabled.

Priority: ⬇️ Low

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

Change: Other

Merge Risk: ⚪ Minimal · up to f4032

The guide accurately describes the configured signing and squash-merge requirements; no material merge risk remains.

Architecture Summary

Architecture risk: 🔵 Low · up to f4032

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 commit-signing instructions covering the default-branch ruleset, SSH signing requirements for people and interactive agents, API-based commits for apps, bots and workflows, and squash merges. It states that unsigned commits on a PR branch block merging, recommends recreating affected branches with signed commits, and says 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 signing guidance, policy context, affected workflows, and documentation-only scope.

• 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 each commit with care,
Then hops through squash merges, light as air.
If unsigned commits block the way,
A fresh signed branch can save the day.
The rules now guide each change we share.}

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