[Feature] Make rojo new port happen on ask

It's not always obvious a new port is being used. We should either ask the user, skip with --interactive mode, or allow a --port cli.

Start by locating the CLI entry point and the code that invokes `rojo new` or selects a port. Clarify whether the intended behavior is prompting, skipping in interactive mode, or adding a `--port` option; done means one agreed behavior is implemented and its CLI behavior is covered by tests.

Written by the indexing model from the issue text.