Setup Sandbox

This scaffolds the initial directory structure for a Recoup sandbox by fetching organizations and artists via the CLI and creating a workspace folder for each one. It's meant to run once, right after a sandbox is created and before any work begins. The skill checks for an existing orgs/ directory first so you don't duplicate things, then creates artist folders using the exact slug from the API and drops a RECOUP.md marker file in each one with the artist's name, slug, and UUID. That marker is what ties the workspace back to the platform. It handles both personal and org API keys by conditionally passing the account flag. One less manual setup step when spinning up new environments.