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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Run ID: c402bd43-52b1-4cc5-84af-916074aa524f

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• CONTRIBUTING.md

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🔇 Additional comments (1)

CONTRIBUTING.md (1)

122-137: LGTM!

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📝 Summary

Summary by CodeRabbit

• Documentation
  • Added guidance requiring signed commits for changes to the default branch and pull request branches.
  • Documented signing requirements for people, agents, apps and workflows, along with squash merging and steps for resolving unsigned commits.

Walkthrough

CONTRIBUTING.md adds instructions for signed commits, squash merges, and handling unsigned commits on pull request branches.

Changes

Signed commit contribution guidance

Layer / File(s)	Summary
Signing and merge instructions CONTRIBUTING.md	Specifies signing requirements for people, interactive agents, apps, bots, and workflows. Requires squash merges, describes how to recreate affected branches with signed cherry-picks, and states that rebase-merge is disabled.

Priority: ➖ Normal

Estimated code review effort: 1 (Trivial) | ~5 minutes

Change: Other

Merge Risk: ⚪ Minimal · up to 6373a

The guide makes signing and squash-merge expectations explicit, consistent with the checked-in signing policy and Dependabot flow. GitHub enforcement and rebase settings remain unverified, but no actionable mismatch or merge blocker is established.

Architecture Summary

Architecture risk: 🔵 Low · up to 6373a

The change affects 1 system.

Changed systems: CONTRIBUTING.md

Architecture concerns
No architecture-level concerns identified.

Review details

Systems and components

• observed — CONTRIBUTING.md (service) was modified; 1 changed file maps to changed impact.

Before / after behavior

• observed — Modified behavior in CONTRIBUTING.md: Adds contribution instructions requiring signed commits on the default branch, distinguishing SSH signing for people and interactive agents from API-based commits for apps, bots, and workflows. Requires squash merges because unsigned commits on a PR branch block merging; directs contributors to recreate such branches with signed cherry-picks and states 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.md.
Description check	✅ Passed	The description directly explains the documentation change, its signing policy context, and the affected contribution workflow.
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 a commit with care
Then checks the merge rules in the air
With squash, the branch goes hopping by
Signed cherry-picks reach the sky
The guide is clear; the hare can rest}

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

✨ Finishing Touches 💡 1

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