How does the built-in Installer bootstrap work?
The core downloads the full Installer only when it is first needed and automatically resumes the original install request.
Bare core
On a clean Bare core, install help first adds Installer to .lil.php. The continuation state survives the reload, so the same request then installs Help without asking you to type it again.
Preset builds
Toolkit downloads no longer embed Installer, Run or Include just to start setup. The core reads the adjacent #lil setup.lil, bootstraps Installer through the same path, installs the selected modules and removes setup.lil only after the whole setup succeeds.
Examples
install help