Raycast "Switch Output Device" / "Switch Input Device" commands

[janthoXO]

Future work, DESIGN.md sections 7.4 and 13.

Device picker commands in the Raycast extension:

1. Run the app binary in CLI mode (list output or list input) to get devices, status and order.
2. Show a Raycast list.
3. On selection, open klangladder://switch?scope=...&uid=....
4. Show a HUD such as "Output: AirPods Pro".

Depends on: CLI mode (R1), URL scheme write commands, and the Raycast extension base.