Manage inputs from both VS Code commands and CLI

[hughess]

In some cases, users will interact with both the VS Code extension commands and the Evidence CLI. This can result in unexpected behaviour in the extension.

An example is clicking the play button to start the dev server, then stopping it with Ctrl + C. In this case, the dev server will stop, but the VS Code status bar (play button) will not receive the information that the server has stopped, and will continue to show the "disconnect" icon.

This issue should cover the most frequent situations that are likely to occur.

[hughess]

I think this becomes less likely once we have keyboard shortcuts for starting/stopping the server