Self-update

kya update    # self-update to the latest @shield-agent/kya

• kya start shows a notice when a newer npm version exists. The check is cached for 24 hours and never blocks the command.
• Node 22+ is required (24 recommended). Node 20 and 21 are unsupported but work, with a one-line warning; Node 18 and older are not supported. Below 22 the CLI offers to install Node 24 (volta / fnm / nvm / brew), reinstall itself, and finish the command; declining prints a warning and continues.

Fresh install instead: /install.