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.

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ℹ️ Recent review info

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Configuration used: Organization UI

Review profile: ASSERTIVE

Plan: Advanced

Run ID: 9ee654cc-e6a4-4d5b-9a25-f8dfe3b8dd0e

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Reviewing files that changed from the base of the PR and between dbeee8a and 1c10b3f.

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• CONTRIBUTING.adoc

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🔇 Additional comments (3)

CONTRIBUTING.adoc (3)

160-165: LGTM!

Also applies to: 166-167, 187-187

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156-157: 🔒 Security & Privacy | 🛡️ Detected with Advanced Tier

The signature-enforcement statement is supported by active default-branch rulesets. Require-Signed-Commits and default-branch-protection both apply required_signatures to ~DEFAULT_BRANCH. The optional API call in scripts/governance/apply-branch-protection.sh does not contradict these rulesets.

Likely an incorrect or invalid review comment.

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169-169: 🔒 Security & Privacy | 🛡️ Detected with Advanced Tier

Check the repository's rebase-merge setting. The branch-protection script does not set allow_rebase_merge, and the available API access returns null for this field. Confirm with repository-admin access that rebase merging is disabled. If it is enabled, disable it because rebase merging can add rewritten unsigned commits to the default branch.

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📝 Summary

Summary by CodeRabbit

• Documentation
  • Updated contribution guidance to cover commit signing requirements, signing methods, and the use of squash merges.
  • Changed the pull request checklist to ask for signed commits rather than specifically GPG-signed commits.

Walkthrough

The contribution guide now describes commit-signing requirements, supported signing methods, and merge rules. The pull request checklist now requires signed commits rather than GPG-signed commits.

Changes

Contribution guidance

Layer / File(s)	Summary
Commit-signing guidance and checklist CONTRIBUTING.adoc	The guide requires signed commits to the default branch under a ruleset. It describes SSH signing for people and interactive agents, API-based commits for apps, bots and workflows, and squash merges. It also states that unsigned commits on the pull request branch block merging and that rebase-merge is disabled. The checklist now requires signed commits.

Priority: ⬇️ Low

Estimated code review effort: 1 (Trivial) | ~5 minutes

Change: Other

Merge Risk: ⚪ Minimal · up to 1c10b

The updated signing guidance is mergeable with normal checks. No concrete workflow regression was established, although the stated squash and rebase settings could not be independently confirmed.

Security Architecture Review

Security architecture risk: 🔵 Low · up to 1c10b

This changes contribution instructions, not enforcement. No introduced security weakness was established, but the stated merge restrictions could not be fully checked against active repository settings.

Retained concerns
No architecture-level concerns identified.

Security review details

Security Blast Radius

• inferred — The assessed boundary is contribution admission to this repository's default branch. The documentation change does not demonstrate additional credential authority, cross-repository access, deployment access, or a broader attacker-controlled execution path.

Security Findings and Attack Paths

• observed — The supplied security assessment retains no findings. The disabled-rebase candidate remains deferred because the active allow_rebase_merge value is unavailable; that uncertainty does not establish an exploitable bypass or a regression introduced by this PR.

Trust Boundaries and Controls

• observed — Supplied verification reports active default-branch rulesets requiring signed commits and rejects the corresponding missing-enforcement candidate. This is counterevidence to a signing-enforcement gap, but does not independently verify every documented merge restriction or bypass setting.

Resilience and Maintainability Implications

• observed — The existing script continues after a failed required-signatures POST and prints a completion message. This pre-existing recovery behavior cannot establish successful signature enforcement by that script, but it neither proves an active ruleset failure nor constitutes an introduced PR concern.

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title clearly identifies the documentation change and names the affected file.
Description check	✅ Passed	The description directly explains the signed-commit guidance added to CONTRIBUTING and matches the documented changes.
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.

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_{A rabbit checks each commit's mark,
Then hops through rules from dawn till dark.
SSH keys shine, APIs pass,
Squash merges keep the branch in class.
The checklist blooms; the hare says, “Done!”}

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