[NFR]: crest new writes a docker launcher script #29

Summary

crest new writes a small shell script into the project. It runs crest in the app container, so a user without PHP on the host can type ./crest route:list.

Why

A user with docker and no PHP on the host cannot run a global crest. The hand-off (#27) and the runtime key (#28) need a global crest, so they do not help this user. Today the user types docker compose exec app vendor/bin/crest ... for each command. A small shell script that does not need PHP will help.

Scope

• The script runs docker compose exec <service> vendor/bin/crest "$@" and returns the exit status.
• The service is the app service of the generated docker-compose.yml, or the runtime key of crest.php after [NFR]: crest init and a required crest.php #28.
• Without a TTY (for example in CI), it uses docker compose exec -T.
• A new stub (project-launcher), with the executable bit.
• The generated README and the docs show it.

Open

• The file name and place (for example ./crest in the project root).
• Windows: a .cmd or PowerShell version.
• Does crest init ([NFR]: crest init and a required crest.php #28) also write it?

Done when

On a host with docker only, ./crest route:list in a generated project runs in the container and returns its exit status.

Related: #27, #28, #16.