Test curl-pipe-sh installers inside a throwaway Docker container

To test an installer as a fresh user without touching the developer's global npm packages, ~/.claude hooks or ~/.config, run it in a disposable node:20-bookworm container with an empty HOME and a different git identity. If the installer hardcodes localhost:PORT, forward the port inside the container with socat TCP-LISTEN:8100,fork,reuseaddr TCP:host.docker.internal:8100. Feed prompts over stdin, then dump the files it wrote. Afterwards, confirm on the host that the real config and the settings file timestamp did not change. Rewriting the install URL for localhost is fine, but note that it differs from a real customer hostname.