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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🔇 Additional comments (1)

CONTRIBUTING.adoc (1)

22-37: LGTM!

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📝 Summary

Summary by CodeRabbit

• Documentation
  • Documented the signed-commit requirements for changes reaching the default branch, including signing methods for people, agents, apps and workflows.
  • Clarified that pull requests must be squash-merged and that unsigned commits prevent merging.

Walkthrough

The contribution guide now defines signed-commit requirements for contributions and specifies how unsigned commits affect pull request merging.

Changes

Signed-commit policy

Layer / File(s)	Summary
Commit signing and merge requirements CONTRIBUTING.adoc	The guide specifies signing requirements for people, interactive agents, apps, bots and workflows. It requires squash merges, rejects unsigned commits, and states that affected branches must be recreated and submitted in a new pull request.

Priority: ⬇️ Low

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

Change: Other

Suggested reviewers: metadatastician

Merge Risk: ⚪ Minimal · up to 0c25e

The signed-commit and squash-merge guidance is supported by the active ruleset and GitHub’s documented checks. The available evidence does not establish whether rebase merging is disabled, but no merge blocker is verified.

Security Architecture Review

Security architecture risk: 🔵 Low · up to 0c25e

The change documents signing and merge requirements without granting new privileges or changing executable controls. No introduced security weakness was established, but the claimed bypass restrictions and merge-method configuration remain unverified.

Retained concerns
No architecture-level concerns identified.

Security review details

Security Blast Radius

• inferred — The policy concerns contributor and automation commit paths into this repository’s default branch. The inspected change does not expand service, tenant, credential, or data-store authority.

Trust Boundaries and Controls

• observed — People and interactive agents must use GitHub-registered SSH signing keys and verified committer email. Apps, bots, and workflows must use API-mediated commit creation instead of pushing local commits. These are distinct documented authenticity paths, not new grants of repository write permission.
• observed — An earlier source inspection reported an active required-signatures ruleset targeting the default branch. Actual bypass permissions and enabled merge methods were not established, so the document’s stronger enforcement assertions remain only partially corroborated.

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title clearly identifies the main change: adding a Signed commits section to CONTRIBUTING. It is concise and specific.
Description check	✅ Passed	The description directly explains the documentation change, its signing policy requirements, and the affected contributor guidance.
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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✨ Finishing Touches 💡 1

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