Don't start a debug session in VS code on initial terminal open

[connor4312]

Right now you're in a weird state when the terminal is open, where you're apparently in a debug session with the red action bar and debug overlay, but no running program. We should not trigger a debug session in VS code until a child attaches.

[connor4312]

To verify, open the JavaScript Debug Terminal, see that VS Code doesn't enter debug mode. Run a program like node test.js, observe that it enters debug mode and exits debug mode when the process exits, keeping the terminal open.