Openshell gateway is being deleted on last sandbox deletion

[ivobrett]

Remove cleanupNemoClawSandbox and its helper isNemoClawSandboxNotRegistered. That function called nemoclaw destroy --yes which triggers gateway deletion. This is problematic if running openshell controller on a host where you want to keep the openshell gateway running after the last sandbox is deleted

[mmckeen-nv]

POST /api/sandbox/delete only calls openshell sandbox delete now. I will push code later today.