Currently variant states be synchronized w/ server-side via cookie, sent along w/ the template-annotations/definitions request. Will not work with separate origins & third-party cookies ban

• Start managing page-editor state on the client side (SPA/standalone page-editor), e.g. like scroll position
• intercept variant selection event before we communicate to the outer frame via postmessage?

If keeping state using browser's sessionStorage, selection is lost when browser tab is closed. This is expected and acceptable. Alternatively localStorage may be more persistent.