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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Plan: Advanced

Run ID: 14aa5956-4245-4efb-8965-20776ee8f1eb

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Reviewing files that changed from the base of the PR and between 0a00bcf and 8d08035.

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• CONTRIBUTING.adoc

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📝 Summary

Summary by CodeRabbit

• Documentation
  • Added contribution guidance requiring signed commits on the default branch, with specific signing requirements for people, agents, apps, bots and workflows.
  • Clarified that contributors must squash-merge; unsigned commits block merging, and rebase-merging is unavailable.

Walkthrough

CONTRIBUTING.adoc now sets signed-commit requirements for changes reaching the default branch. It describes signing methods for people, interactive agents, apps, bots, and workflows, and states the rules for unsigned PR branches and squash merging.

Changes

Signed commit policy

Layer / File(s)	Summary
Contributor signing and merge requirements CONTRIBUTING.adoc	Adds SSH signing and verified-email requirements for people and interactive agents. Apps, bots, and workflows must use the API or the estate signed-push action. The guidance states that unsigned PR branches block merging and that contributors must squash-merge.

Priority: ⬇️ Low

Estimated code review effort: 2 (Simple) | ~5 minutes

Change: Other

Suggested reviewers: metadatastician

Merge Risk: ⚪ Minimal · up to 8d080

The signing guidance introduces no demonstrated merge-blocking issue. The documentation change is mergeable subject to normal checks.

Security Architecture Review

Security architecture risk: 🔵 Low · up to 8d080

Only contribution guidance changes, with no implementation or permission changes. The signing requirements clarify contributor responsibilities, but the repository settings and referenced automation were not verified, so their documented guarantees remain unconfirmed.

Retained concerns
No architecture-level concerns identified.

Security review details

Security Blast Radius

• observed — The policy addresses commits reaching this repository's default branch. The PR contains no changes to credentials, IAM permissions, application authorization, deployment configuration, or data access.

Trust Boundaries and Controls

• observed — People and interactive agents are instructed to use a GitHub-registered SSH signing key and verified committer email. Apps, bots, and workflows are instructed to use API-mediated commits for GitHub signing. These are documented procedures, not newly implemented controls or evidence of additional authority.

🚥 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 Signed commits section added to CONTRIBUTING.
Description check	✅ Passed	The description directly explains the docs-only change, its signing policy context, and the contributor guidance added to CONTRIBUTING.
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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Then hops along the squash-merge trail.
The branch is ready, signatures set,
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✨ Finishing Touches 💡 1

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