Refactor: Separate output formatting from command logic in `traffic_ctl`

# Refactor: Separate output formatting from command logic in traffic_ctl

## Summary

Output formatting responsibilities are split between `CtrlCommand` subclasses and `BasePrinter` subclasses. The intended design is that commands handle logic/RPC and printers handle output formatting. In practice, both sides do formatting and neither fully owns it.

This was the initial goal, but it got sidetracked — it was easy to implement the text formatting as early as possible in the command layer, and over time that pattern spread.

## Desired state

Commands should produce structured data (or call domain-level output methods) and **never** construct user-facing text, check format flags, or reference concrete printer types. The output layer should fully own how data is rendered for each format.
This was the initial goal, but it got side tracked