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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Reviewing files that changed from the base of the PR and between 14d4eaf and abd339a.

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• .github/CONTRIBUTING.md

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🔇 Additional comments (1)

.github/CONTRIBUTING.md (1)

123-138: LGTM!

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📝 Summary

Summary by CodeRabbit

• Documentation
  • Added guidance on commit-signing requirements, including accepted signing methods for people, agents and automated workflows.
  • Clarified that unsigned commits must be recreated as signed commits and that pull requests are merged using squash merges.

Walkthrough

The contribution guide adds signed-commit requirements for people, interactive agents, apps, bots and workflows. It also explains how unsigned commits affect merging and states that pull requests must use squash merges.

Changes

Signed commits

Layer / File(s)	Summary
Signing and merge requirements .github/CONTRIBUTING.md	The guide specifies SSH signing for people and interactive agents, API-based signing for apps, bots and workflows, and squash merges. It states that unsigned commits block merging and must be recreated as signed commits.

Priority: ⬇️ Low

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

Change: Other

Merge Risk: ⚪ Minimal · up to abd33

No actionable issue is established in the signed-commit guidance that warrants delaying this documentation change.

Architecture Summary

Architecture risk: 🔵 Low · up to abd33

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 signed-commit requirements and instructions: people and interactive agents use a GitHub-registered SSH signing key and verified committer email; apps, bots and workflows use the API or estate signed-push action rather than pushing local commits. PRs must be squash-merged because the ruleset checks every branch commit; unsigned commits block merging and must be recreated with signed commits, while rebase-merge is disabled.

🚥 Pre-merge checks | ✅ 4 | ❌ 1

❌ Failed checks (1 warning)

Check name	Status	Explanation	Resolution
Description check	⚠️ Warning	The description explains the change and its rationale, but it omits the required template sections for the quality checklist, testing, and screenshots. It also does not use the required Summary, Chang…	Update the description to follow the repository template. Add the Summary, Changes, RSR Quality Checklist, Testing, and Screenshots sections. Complete each applicable checklist item and state the test result, or mark a section as not applic…

✅ Passed checks (4 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title clearly and concisely describes the main documentation change.
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.

Full details: Description check

Explanation

The description explains the change and its rationale, but it omits the required template sections for the quality checklist, testing, and screenshots. It also does not use the required Summary, Changes, or Testing headings.

Resolution

Update the description to follow the repository template. Add the Summary, Changes, RSR Quality Checklist, Testing, and Screenshots sections. Complete each applicable checklist item and state the test result, or mark a section as not applicable with a reason.

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_{A rabbit signs each commit with care,
Then checks the branch before the merge.
Squash commits bring the changes through,
Signed and ready, neat and true.
The guide now shows the way to go.}

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