docs: fix textlint terminology error in engineering roadmap

- Update "run-time" to "runtime" in docs/SENTINEL_ENGINEERING_ROADMAP_V2.4.md.
- Resolve NATURAL_LANGUAGE linting failure in GitHub Actions.

Verified against repository-wide textlint rules.

Co-authored-by: OneFineStarstuff <87420139+OneFineStarstuff@users.noreply.github.com>

Author: google-labs-jules[bot]