Configure the Cube agent

Mostly know-how rather than commands. Two CLI calls read the current state; everything else is writing markdown into the data model, which means the dev-mode workflow from cube-build-model applies.

Preflight

command -v cube >/dev/null || echo "Cube CLI not installed: curl -fsSL https://raw.githubusercontent.com/cube-js/cube/master/install-cli.sh | sh"
cube whoami || echo "Not authenticated. Interactive: cube login. Headless: set CUBE_API_URL + CUBE_API_KEY."
cube context list

See what's configured