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

⚙️ Run configuration

Configuration used: Organization UI

Review profile: ASSERTIVE

Plan: Advanced

Run ID: 5bb6c2d1-efd2-4933-b783-7fe7f5b55a38

📥 Commits

Reviewing files that changed from the base of the PR and between e45f3cd and c33e253.

📒 Files selected for processing (2)

• .github/CONTRIBUTING.md
• CONTRIBUTING.adoc

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🔇 Additional comments (4)

.github/CONTRIBUTING.md (3)

328-335: LGTM!

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336-339: 🎯 Functional Correctness

The repository merge settings and applicable ruleset are not available in the supplied source. The squash-only requirement cannot be confirmed from the documentation files alone.

---

326-327: 🎯 Functional Correctness

The concern is refuted. The repository has an active Require-Signed-Commits ruleset with required_signatures applied to ~DEFAULT_BRANCH. The statements in both documents describe a live repository control.

CONTRIBUTING.adoc (1)

118-125: LGTM!

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📝 Summary

Summary by CodeRabbit

• Documentation
  • Updated contribution guidance to require signed commits for changes reaching the default branch. Unsigned commits on pull-request branches prevent merging.
  • Added signing instructions for people, interactive agents, apps, bots and workflows, including the use of verified committer email addresses.
  • Explained how to replace unsigned commits with signed cherry-picks and submit a new pull request.
  • Clarified that pull requests must use squash merges; rebase merges are disabled.

Walkthrough

Both contributor guides now document signed-commit requirements, signing methods for different contributor types, and merge rules.

Changes

Signed-commit policy

Layer / File(s)	Summary
Document signing and merge rules .github/CONTRIBUTING.md, CONTRIBUTING.adoc	Both guides require signed commits. They describe signing methods for people and automated contributors, require squash merges, explain how unsigned commits affect merging, and provide instructions to recreate a branch with signed commits.

Priority: ⬇️ Low

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

Change: Other

Merge Risk: ⚪ Minimal · up to c33e2

The guides document signed-commit requirements and contribution workflows without changing runtime behavior. No concrete merge-blocking issue is established.

Security Architecture Review

Security architecture risk: 🔵 Low · up to c33e2

The change documents signing and merge requirements without modifying permissions or enforcement. No introduced security weakness was established, but the stated repository controls and automation signing behavior could not be independently verified.

Retained concerns
No architecture-level concerns identified.

Security review details

Security Blast Radius

• inferred — The supported impact is contributor behavior and expectations about default-branch admission. The inspected change does not itself expand credentials, service access, or deployment authority.

Trust Boundaries and Controls

• observed — The documentation places commit signing at the contributor-to-default-branch trust boundary and describes GitHub as the signing authority for API-created automation commits. It does not supply evidence establishing the effective ruleset, bypass permissions, merge settings, or external signing action behavior.

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title clearly and concisely summarises the main documentation change: adding a Signed commits section to CONTRIBUTING files.
Description check	✅ Passed	The description directly explains the signed-commit guidance, affected contributor workflows, merge requirements, and docs-only scope of the 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 signs each commit with care
SSH keys tucked beneath one ear
Squash merges carry changes through
Unsigned branches get signed anew
Then hops away with carrots to share}

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