docs: add PR body requirements section to CONTRIBUTING.md

[kitcommerce]

Fixes #924

Client impact

None (docs only).

Verification Plan

Section is present and readable in CONTRIBUTING.md

[kitcommerce]

Architecture Review

Verdict: PASS

Adding a "Pull Request Body Requirements" section to CONTRIBUTING.md is the right location for this documentation. The addition is appropriately scoped — it describes a process requirement and links it to the tooling introduced in companion PRs (#1120, #1122).

No coupling concerns. Docs change only.

[kitcommerce]

Simplicity Review

Verdict: PASS

Minimal, direct prose. The section covers what's required, gives a brief rationale for each field, and provides a concrete example. The warning about closure without review is appropriately firm without being verbose. Nothing extraneous.

[kitcommerce]

Security Review

Verdict: PASS (N/A)

Markdown documentation only. No code, no credentials, no attack surface. Nothing to assess.

[kitcommerce]

Rails Conventions Review

Verdict: PASS

Documentation-only PR. The new section uses #### heading level, which is consistent with CONTRIBUTING.md's existing heading hierarchy. Bold field names with em-dash descriptions match the existing style. Placement and tone are appropriate for contributing guidelines.

[kitcommerce]

Rails Security Review

Verdict: PASS

Findings

No security findings. This PR adds documentation only (a new section to CONTRIBUTING.md describing PR body requirements). No Ruby code, views, controllers, routes, or configuration files are changed.

Recommendations

None — no security surface affected.

[kitcommerce]

Test Quality Review

Verdict: PASS

Findings

• This is a documentation-only change (additions to CONTRIBUTING.md describing required PR body sections).
• No executable code was added or modified, so there is nothing to test.
• Documentation changes do not require automated test coverage.

Recommendations

• No action needed. Docs-only PRs are appropriately out of scope for test quality review.

[kitcommerce]

Database Review

Verdict: PASS

Findings

No database-related changes detected. This PR adds documentation to CONTRIBUTING.md only — no migrations, schema changes, queries, or ActiveRecord modifications.

Recommendations

None.

[kitcommerce]

Wave 3 Quality Review

Frontend — PASS
Docs-only change in CONTRIBUTING.md. No UI code, styles, templates, or JS behavior changed.

Accessibility — PASS
Markdown structure is clear and readable. The added section uses the existing heading hierarchy, descriptive labels, and a fenced code block/example without introducing accessibility regressions.

Performance — PASS (N/A)
Documentation-only change. No runtime, query, asset, or rendering impact.

Documentation — PASS
The new section is scoped appropriately for CONTRIBUTING.md, explains both required PR body sections clearly, and includes a concrete minimal example reviewers can follow.