[ekalinin]

Summary

Fixes #176: CI runs the tests with bats 1.6.0, while the latest bats-core release and
Homebrew are at 1.14.0. Every CI run also has the warning Node.js 20 is deprecated ... forced to run on Node.js 24: actions/checkout@v2, mig4/setup-bats@v1.

Changes in .github/workflows/ci.yml:

• "Setup bats": mig4/setup-bats@v1 (last release in 2020) with bats-version: 1.6.0
  is replaced with the official bats-core/bats-action@4.1.0 with
  bats-version: 1.14.0.
  • An exact version, not latest: the action caches bats with the key
    bats-${{ inputs.bats-version }}, so with latest the key never changes and CI
    would stay on the first cached version.
  • support-install, assert-install, detik-install and file-install are false:
    the tests use their own tests/test_helper.bash.
  • github-token: the action downloads the bats tarball from api.github.com.
• "Check out code": actions/checkout@v2 is replaced with @v7, the version
  pages.yml already uses. The changes from v5 to v7 (Node.js 24, credentials in a
  separate file, no fork PR checkout on pull_request_target / workflow_run) do not
  affect this workflow.
• openspec: the update-ci-bats change (proposal, design, tasks) with
  skip_specs: true, not archived yet. The behavior of gh-md-toc does not change.

The tests and the other workflows do not change.

Not included: dockerimage.yml (actions/checkout@v2, docker/build-push-action@v1),
Dependabot, the remote tests that fail now and then on github.com pages (#179).

Testing

• make test with bats 1.14.0 locally: all 76 tests pass (macOS).
• yamllint -d relaxed and actionlint 1.7.12 report nothing on ci.yml. Before the
  change, actionlint reported the runner of "actions/checkout@v2" action is too old to run on GitHub Actions.
• The CI of this PR is the check of the workflow itself.