21st Design Sync — publish your project's design as a theme Take the design a project already ships (its light + dark CSS variables) and publish it to the public 21st.dev theme library so anyone can preview, bookmark, and apply it. Under the hood this is one CLI call: . Pre-flight (always) 1. Auth needs a real API key. is a management endpoint: it accepts a key only , not a session token. Get one at https://21st.dev/mcp (or https://21st.dev/settings/api-keys ) and pass it via or the / env var. If the user has no key, point them there — don't try to mint one. 2. The CLI is the unified (bin ).…