Run in detached mode

This is now working locally. Going to test more broadly.

I've also stubbed in a Starship prompt module, but it's not working...

Ok! Whole new process handling is now working. See the new commands available in the devshell with '?'.

In short, after refreshing the flake to get the latest, and entering the dev shell with `nix develop` or direnv, there are new commands for starting without the process-compose TUI (text user interface). This is built for running in existing Drupal projects -- the demo still uses the TUI, at least for now.

So, to get started with this, go into a local Drupal copy and either:

nix flake init -t gitlab:project/drupal_flake?host=git.drupalcode.org (new install)

or

nix develop
refresh-flake (existing install).

Then:

start-detached

and then you can follow the URL printed to see your site!

There are a few new shell scripts that start with "pc-", which are wrappers for process-compose:

- pc-status -- check the status of process-compose
- pc-attach -- attach to the TUI (you can detach by pressing the F10 key -- when attached this way this only closes the TUI, it does not shut down the project).
- pc-stop -- Stop the current project
- stop-all -- stop all process-compose processes, including other projects

Finally, there's an extra feature added here -- if you use the Starship prompt - https://starship.rs/ - you can install a starship module that will show when you are in a Drupal-flake project that is running. When process-compose is running in your project, you'll see a waterdrop and snowflake emoji, followed by your project name, right in the prompt:

... you can install it in your user profie using "setup-starship-prompt".