source-control:pull-request: emit ## Related + closing-keyword skeleton in create flow

[kyle-sexton]

Lane: work

Triggering example

Issue #462: PRs fail the pr-issue-linkage CI check because nothing scaffolds the required ## Related section + native closing keyword (Closes #N). #462 adds a repo-root .github/pull_request_template.md to cover the web/editor authoring path. This follow-up covers the other half of #462's "and/or": the /source-control:pull-request create flow.

Observed

The create flow assembles a PR body from its own internal template (plugins/source-control/skills/pull-request/reference/create.md §2.4.1). Because gh pr create --body "..." fully overrides .github/pull_request_template.md (cli/cli#10751), agent-driven PRs never see the repo template. The assembled body has ## Summary / ## Test plan but does not scaffold a ## Related section, and the closing keyword is only conditionally present via ${CLOSES_LINE}.

Expected

The create flow should emit a ## Related section and a closing-keyword line as part of its assembled skeleton, mirroring the exact contract enforced by the pr-issue-linkage reusable workflow (non-empty ## Related + native closing keyword or the documented opt-out marker), so agent-authored PRs satisfy the gate without a red-CI round-trip.

Category

improvement

[kyle-sexton]

This was generated by AI during triage. · Category: improvement · Priority: priority: high (source-control north-star; avoids red-CI round-trips on agent-authored PRs). Routed status: ready.

Plan

The /source-control:pull-request create flow assembles a PR body from its own internal template and passes it via gh pr create --body, which fully overrides .github/pull_request_template.md — so agent-authored PRs never see the repo template and fail the pr-issue-linkage gate. This covers the create-flow half of #462 (the repo template covers the web/editor half).

Change: the create flow's assembled skeleton emits a non-empty ## Related section and a closing-keyword line (Closes #N, or the documented opt-out marker), mirroring the exact contract enforced by the pr-issue-linkage reusable workflow. The existing ${CLOSES_LINE} conditional is promoted so the closing keyword / opt-out is always scaffolded, not conditionally present.

Acceptance

• A PR created through the /source-control:pull-request create flow satisfies pr-issue-linkage on first push (non-empty ## Related + native closing keyword or opt-out marker) with no red-CI round-trip.
• The body shape stays owned by pull-request's template; this only adds the two required scaffolds.

Decision defaulted: scaffold ## Related + always-present closing-keyword/opt-out line in the create flow's assembled body, mirroring the pr-issue-linkage contract — veto before merge