`robotpy deploy` will erase manually installed packages

[virtuald]

If the user specifies --no-deploy or they decline the sync, then they'll never run into this. But for users that want to use a manual workflow, this will be a problem since there isn't a manual deploy process that doesn't do a sync. Thinking about two alternatives:

• Add options to pyproject.toml to say "don't manage the packages on the rio"
• Add a robotpy installer deploy which only deploys the code, and doesn't do all of the fancy things that the robotpy deploy command does

... I'm sorta attracted to the second option because I'd rather not have configuration options. Maybe call it robotpy installer only-deploy or robotpy installer deploy-only? Sorta like with git having plumbing and porcelain commands.