Add GitHub Actions workflow to auto-close stale maintainer-scrap issues

[dyoshikawa]

Motivation

• Reduce manual triage by automatically closing issues labeled maintainer-scrap that have not been updated for a month.
• Provide a safe, auditable scheduled job that maintainers can also trigger manually.

Description

• Add a new workflow file at .github/workflows/auto-close-maintainer-scrap-issues.yml that runs daily (UTC 00:00) and supports workflow_dispatch manual runs.
• Use actions/github-script@v8 to list open issues with the maintainer-scrap label, skip pull requests, and close issues whose updated_at is >= 30 days old while logging actions.
• Grant minimal permissions required (contents: read, issues: write).

Testing

• Ran pnpm cicheck, which includes formatting, linting, type checks, unit tests, and content checks, and it completed successfully.
• The test suite ran via vitest and reported all tests passing (4901 tests passed).
• Content checks (cspell and secretlint) completed successfully as part of pnpm cicheck.

---

Codex Task

[Copilot]

Pull request overview

Adds a scheduled GitHub Actions workflow to reduce maintainer triage by automatically closing stale issues labeled maintainer-scrap, with an option to trigger the job manually.

Changes:

• Introduces a new scheduled + manual workflow to scan open maintainer-scrap issues.
• Filters out pull requests and closes issues whose updated_at is ≥ 30 days old.
• Uses minimal repository permissions (contents: read, issues: write) and logs each action.

[Copilot]

actions/github-script is referenced by a mutable tag (@v8). In this repo, workflows pin actions to an exact commit SHA for supply-chain security and reproducibility (e.g., actions/checkout@<sha> in other workflows). Please pin actions/github-script to a full-length commit SHA (with an inline comment noting the corresponding version).

Suggested change

	uses: actions/github-script@v8
	uses: actions/github-script@60a0d83039c74a4aee543508d2ffcb1c3799cdea # v8