Prerelease for the Node 26 SEA packaging modernization.
Changes:
- Modernize the Node SEA build around Node 26, including the ESM SEA entrypoint and embedded Web UI assets served from node:sea.
- Add GitHub Actions SEA artifact builds for Linux, Windows, and macOS x64/arm64, with the known Darwin x64 smoke path skipped.
- Move GitHub Actions toward Node 24 execution and pin action SHAs.
- Update ESLint to v9 flat config while keeping the previous practical rule surface.
- Clean up deprecated lint/build dependencies and fix the Docker build Web UI helper copy.