Chutes mining pool in testing, public chute deployment changed

A closed-participation mining pool is being tested to ensure reliable compute supply for the subnet. Separately, public chute deployment via CLI has been restricted—users must now create private chutes and use the `chutes share` command instead, requiring special permissions to publish publicly.

• •Closed mining pool in testing phase to simplify participation
• •Public chute deployment now restricted; private + share command required