more control over processes

There is very little we can do when it comes to killing the main process, restarting it, or even counting how many processes are currently running.

Let's suppose I can only have `1` instance running because I'm __limited by external apis__. When you click on the project weblink it might spawn a new process even if another one is already running (this is probably because of web servers routing). I would love to have an option in the settings that limits this behaviour (*in the sense that if it finds a process running it won't start a second one*).

I also would love you guys to enable the following features:
```js
Deno.pid
Deno.ppid
Deno.exit(...)
```

I would also advice you to have a kill switch on the main deploy interface to kill the processes in case of issues.

The issue names no files, tests, or entry points. Start by clarifying whether process limits, Deno.pid/ppid/exit, and a deployment kill switch belong in scope, then inspect the deployment process lifecycle, settings, and main deploy interface. Done requires agreed behavior and tests or acceptance criteria for each selected capability.

Written by the indexing model from the issue text.