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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🔇 Additional comments (1)

CONTRIBUTING.adoc (1)

307-322: LGTM!

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📝 Summary

Summary by CodeRabbit

• Documentation
  • Updated contribution guidance to require signed commits with a GitHub-registered SSH signing key and verified committer email for changes reaching the default branch.
  • Clarified that apps, bots and workflows must use the API or the approved signed-push action instead of pushing local commits.
  • Documented that pull requests must be squash-merged. Unsigned commits on a pull-request branch block merging; contributors must create a new branch with signed cherry-picks and submit a new pull request. Rebase merging is unavailable.

Walkthrough

The contribution guide adds a signed-commit policy. It describes signing requirements, commit creation for apps and workflows, squash merging, and how to handle branches with unsigned commits.

Changes

Contribution policy

Layer / File(s)	Summary
Document signed-commit requirements CONTRIBUTING.adoc	The guide requires signed commits and verified committer email for people and interactive agents. It directs apps, bots and workflows to use the API or the estate signed-push action. It also specifies squash merging and how to handle branches with unsigned commits.

Priority: ⬇️ Low

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

Change: Other

Merge Risk: ⚪ Minimal · up to f1e0e

The change adds signed-commit guidance; no concrete merge-blocking failure is established, so it appears ready for normal checks.

Security Architecture Review

Security architecture risk: 🔵 Low · up to f1e0e

The change is documentation-only and does not demonstrate weakened signing enforcement. However, the new guidance conflicts with the existing signing guide, and the stated repository enforcement settings remain unverified.

Retained concerns

• Low · maintainability · observed: Repository guidance now disagrees on supported signing methods and whether feature-branch commits must be signed. This leaves contributors and maintainers with inconsistent instructions for satisfying the commit-integrity control. The external estate policy may resolve precedence, but that precedence and effective enforcement were not verified.

Security review details

Security Blast Radius

• inferred — The demonstrated impact is on repository contribution and merge-policy interpretation. The documentation change does not establish increased runtime privileges, tenant exposure, or a new commit-signing bypass.

Trust Boundaries and Controls

• observed — The guidance assigns signing-key and email configuration to human contributors and interactive agents, while assigning automation commit creation to API paths that it states are signed by GitHub. This documents an identity distinction without changing the implementation of either path.

Resilience and Maintainability Implications

• observed — The retained signing guide recommends gitsign and permits GPG, whereas the new contribution section prescribes SSH. The documents also disagree about feature-branch signing, creating control-policy ambiguity rather than a demonstrated cryptographic weakness.

🚥 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 signed-commit guidance to CONTRIBUTING.
Description check	✅ Passed	The description directly explains the signing guidance added to CONTRIBUTING and its policy context.
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,
And checks the email set to share.
Squash the branch, then send it through,
Signed cherry-picks make branches new.
Hops of policy guide the way.}

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