Client commands should be plumbed into the command handler

[Chaosvex]

At the moment, the command handling code is temporary for the sake of adding other functions, but it needs to be plumbed into the existing command system.

Ideally, it'd be possible to be able to reuse the same set of registered commands as the console but with gating (the flags were added with that intention) but given the different output methods and different async considerations, that might not be possible at this point.