2026.18.0 - libs update, reg-open ui update, bug fix

What's Changed

• DEV-870 Migrate CI to GitHub Actions and modernize build tooling by @randyhoulahan in #41
• DEV-872 Group open registration meetings by parent conference with agenda-prefix color coding by @randyhoulahan in #44

Full Changelog: 2024.34.0...2026.18.0