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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• CONTRIBUTING.adoc

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🔇 Additional comments (1)

CONTRIBUTING.adoc (1)

112-127: LGTM!

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📝 Summary

Summary by CodeRabbit

• Documentation
  • Added contribution guidance requiring signed commits on the default branch. People and interactive agents must use a registered SSH signing key and verified committer email.
  • Documented that apps, bots and workflows must create signed commits through the API or approved action.
  • Contributors must squash-merge pull requests. Unsigned commits on a pull request branch block merging, and rebase merging is disabled.

Walkthrough

The contribution guide adds signed-commit requirements for default-branch commits and pull request branches. It also specifies signing methods for different contributors and requires squash merges.

Changes

Signed-commit policy

Layer / File(s)	Summary
Signing and merge requirements CONTRIBUTING.adoc	The guide requires signed commits, sets signing methods for people, interactive agents, apps, bots, and workflows, and describes branch checks and merge restrictions.

Priority: ⬇️ Low

Estimated code review effort: 1 (Trivial) | ~3 minutes

Change: Other

Merge Risk: ⚪ Minimal · up to 2f7b3

The guide documents signing and squash-merge requirements consistent with the referenced policy. No concrete current failure is established, so the change is mergeable under normal checks.

Security Architecture Review

Security architecture risk: 🔵 Low · up to 2f7b3

The change is limited to contribution guidance and introduces no executable permission or deployment changes. Actual enforcement of the documented signing and merge restrictions was not verified; no introduced security weakness was established.

Retained concerns
No architecture-level concerns identified.

Security review details

Security Blast Radius

• inferred — The visible policy scope is contribution to this repository's default branch. The changed document contains no executable expansion of service, tenant, credential, or deployment authority.

Trust Boundaries and Controls

• inferred — The signing paths concern signature provenance. A GitHub signature does not independently establish that an automation caller is authorized to write or merge. The document does not grant new permissions, and actual caller authorization and merge enforcement remain outside the verified evidence.

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Description check	✅ Passed	The description clearly explains the documentation change, its signing policy, and the expected contributor workflow.
Title check	✅ Passed	The title clearly and concisely identifies the main change: adding signed-commit guidance 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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_{A rabbit signs each commit with care,
Then checks each branch before the merge.
SSH keys make the signatures clear,
Squash brings commits safely near.
The rabbit hops; the rules stay there.}

_{Comment @coderabbitai help to get the list of available commands.}

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