polari-isle — polari + isle-mesh as ONE install.

After install, two doors (the membership rule — the running agent IS
membership; the store installs nothing on non-members):
  sudo isle core-install     make this device its own (single-device)
                             isle — ends with the production-security
                             walkthrough (deploy-time passwords/domain/
                             certs; generic self-hosting first, provider
                             post-step after)
  ...or join an existing isle via its bootstrap one-liner
                             (printed by core-install on the core).
