Delivery auto-close-linked

[LeXwDeX]

Closes #519

Why

GitHub's native issue auto-close only fires when a PR carrying Closes #n merges into the default branch (main). This repo delivers into dev first (two-tier Git Workflow), so delivered issues stayed open — #433/#472/#473/#474/#475/#477/#496 all had to be closed manually on 2026-09-03. This adds the dev-layer mirror of auto-close.

What changed

• New .github/workflows/dev-issue-autoclose.yml (sole change): trigger pull_request: types: [closed], job gated on merged == true && base.ref == 'dev' (merges to main keep native auto-close — no overlap). Parses the PR body for the official closing keywords + bare #n (case-insensitive, deduped), guards the shared issue/PR number space (skip PRs, skip nonexistent, skip already-CLOSED — no duplicate comments), closes survivors with gh issue close --reason completed plus an explanatory comment naming the delivery PR. Least privilege (contents: read, issues: write, pull-requests: read), no checkout, no third-party actions, PR body passed only via env: (script-injection safe).

Evidence

• DAG delivery dag_fe5f9b2cb4a9P4dMQwVbLL5pi7 — verify PASS: actionlint exit 0; shellcheck exit 0 on the extracted run block; 11/11 dry-run matrix (PATH-shimmed gh intercepting every write): real bodies fix(test): bound httpapi exerciser teardown and force process exit (#472) #487→{472}, feat(opencode): add warn-only shell silence guard #491→{433}, chore: sync main to dev after v1.0.37 notes fix #497→{496}, chore: sync dev to main for v1.0.39 #518→{517} extracted exactly with skip-closed firing; synthetic mixed-case / multi-ref / PR-ref-skip / zero-ref / closed-skip / not-found-skip all correct; chore: auto-close linked issues when PRs merge into dev #519 still OPEN post-run = zero tracker writes. Review verdict ACCEPT (fingerprint sha256:aceb61ec…acac6; arbiter independently re-inspected 7 load-bearing claims after both review lanes lost supervision with zero findings; synthesizer re-performed V1–V7 first-hand).
• Post-merge acceptance observation: this PR's own merge into dev is expected to fire the new workflow (same-repo pull_request events evaluate workflows at the merge ref) and auto-close chore: auto-close linked issues when PRs merge into dev #519 — the declared live proof, not a gate input.

Checklist

• Why, What changed, and Evidence are filled in.
• specgit finish exits 0.