Get the brand bound to this API key

Returns { brand } — the single brand bound to the API key. Check ready (status === "completed") before calling POST /v1/emails, which returns 422 BRAND_NOT_READY until brand extraction finishes.

Embed the design context in the same call with ?include=identity,emailDesign,imageStyle,logos (comma-separated). identity is the structured brand facts; emailDesign / imageStyle are the markdown design system the email agent follows; logos is the CDN logo set. The paginated image library is a separate read (GET /v1/brand/images).