cc: @alanshaw @Peeja

I would like to propose adding three management commands to Guppy that are currently available in the JS client. These commands are essential for users to verify their subscription status, monitor storage limits, and debug permission issues directly from the terminal.

Proposed Commands
Based on the existing JS client functionality:

plan get :- Displays the billing plan the current account is subscribed to
usage report :- Display report of current space usage in bytes
proof ls :- List proofs of capabilities delegated to this agent