URL scheme write commands (switch, move, enable, disable, delete) #12

Future work, DESIGN.md section 7.3.

Today klangladder:// only supports open. Add write commands for the future Raycast commands:

• switch?scope=output&uid=...
• move up / down / top / bottom
• enable, disable, delete

Trust boundary. Any local app or web page can open these URLs.

• Validate every parameter (scope, UID) against the current state. Only delete disconnected devices (5.1).
• Ignore unknown commands.
• Show a user notification for destructive commands (delete) triggered by URL.
• Add a protocol version to the URLs, and refuse mismatches.