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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Reviewing files that changed from the base of the PR and between 2993600 and eec0537.

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• .github/CONTRIBUTING.md

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🔇 Additional comments (1)

.github/CONTRIBUTING.md (1)

93-93: 🎯 Functional Correctness

The repository ruleset state was not inspected. The claim that this repository actively refuses unsigned pushes cannot be decided from the documentation alone.

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📝 Summary

Summary by CodeRabbit

• Documentation
  • Added guidance on commit signing requirements and merge options for contributions.

Walkthrough

The contribution guide now states that commits reaching the default branch must be signed. It describes signing requirements, commit methods and merge constraints.

Changes

Signed commit guidance

Layer / File(s)	Summary
Commit signing and merge rules .github/CONTRIBUTING.md	The guide specifies signing requirements for people, interactive agents, apps, bots and workflows. It also states that unsigned PR-branch commits block merging and that squash merging is used while rebase merging is disabled.

Priority: ⬇️ Low

Estimated code review effort: 1 (Trivial) | ~2 minutes

Change: Other

Merge Risk: ⚪ Minimal · up to eec05

This documentation-only change is mergeable. The signing instructions are internally consistent, although the stated repository enforcement settings could not be confirmed.

Architecture Summary

Architecture risk: 🔵 Low · up to eec05

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: Added contribution guidance requiring signed commits on the default branch, describing signing requirements for people and interactive agents, API-based commits for apps, bots and workflows, and squash merging. It also states that unsigned commits on a PR branch block merging and that rebase-merge is disabled.

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title clearly and concisely describes the main change: adding a Signed commits section to CONTRIBUTING.
Description check	✅ Passed	The description is directly related to the documentation change and explains the signing policy, affected contributor types, and merge requirements.
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 with care
Signed lines hop along the trail
Squash keeps branches neat and clear
Unsigned changes pause before the gate
The guide now tells the way to go}

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✨ Finishing Touches 💡 1

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