chore(source-control): declare pr_body_required_sections for the PR-body gate

[kyle-sexton]

Summary

Plugin-created PRs in this repo trip the pr-issue-linkage gate because the
source-control plugin's portable default PR body scaffolds only ## Summary
and ## Test plan, omitting the ## Related section this repo requires.

This declares the team-tracked pr_body_required_sections key in
.claude/source-control.md — the plugin's designed per-repo seam
(reference/config-resolution.md) — so /source-control:pull-request create
both drafts a ## Related section and pre-checks it before gh pr create.
The key is a closed list that replaces the plugin's default wholesale, so
the portable Summary / Test plan sections are re-declared alongside
Related.

The closing-keyword / No linked issue half of the gate is a separate,
independent mechanism the plugin already satisfies natively (its create logic
always emits a Closes #N line or a No related issue: opt-out marker); it is
not expressible through this heading-only key, so no attempt is made to encode
it here.

Test plan

• No executable behavior changes; this is a plugin-config data file.
• This PR's own body is the live verification: it carries ## Summary,
  ## Test plan, and a non-empty ## Related section plus the No linked issue marker, so the pr-issue-linkage / pr-issue-linkage required check
  must pass on it.

Related

No linked issue.

This closes no GitHub issue; it is a convention-config change. It exists
because the gate previously tripped on plugin-composed bodies: PR #234 in this
repo and dotfiles #301 in a sibling repo both failed the same
closing-keyword-plus-## Related validation on creation.

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https://claude.ai/code/session_0169XBydnqC5S6bkHDz1TDwL

[claude]

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PR Review

• Gather context and read changed files
• Review diff against CLAUDE.md guidelines
• Post findings

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Reviewed: e6ebc18 — .claude/source-control.md (+6/-0)

This is a clean, correctly-scoped config addition. No blocking findings.

What the change does

Declares pr_body_required_sections in the team-tracked plugin config layer, instructing /source-control:pull-request create to scaffold and pre-check ## Summary, ## Test plan, and ## Related before calling gh pr create. The ## Related section is the piece the plugin's portable default omitted, which was the root cause of the pr-issue-linkage gate failures described in the PR body.

Correctness

• Format matches established convention. The new key uses the same ## heading + body-value pattern as the four existing keys (babysit_loop_stop_mode, etc.). ✓
• Gate alignment is accurate. pr-issue-linkage.yml checks for a non-empty ## Related section via /^##\s+related$/i. Declaring it here causes the plugin to scaffold that section, satisfying that check. ✓
• Closing-keyword half correctly excluded. The gate also requires a closing keyword or No linked issue marker, which is not expressible through a heading-list key. The PR description accurately documents this boundary and notes the plugin already satisfies it natively. ✓
• Self-verification holds. This PR's own body carries all three declared sections with content, plus No linked issue, so the gate must pass on it. ✓
• No CLAUDE.md or REVIEW.md criteria are implicated. No secrets, no authorization paths, no injection surfaces, no atomicity requirements, no SHA-pin concerns. ✓

One thing worth noting (not blocking)

The PR description correctly flags that this key is a closed list — it replaces the plugin's portable default wholesale, meaning Summary and Test plan must be re-declared here (which they are). The tradeoff is that any new section the plugin adds to its default in the future won't be inherited; it would need a manual update here. That's an intentional design decision and is documented, but it's worth keeping in mind if the plugin evolves.

Overall: LGTM. The change is minimal, purposeful, and the PR body itself is live proof that it works.