Read a version link (public)

What the page at https://zindex.ai/d/{ref} shows, and with .svg or .png the image itself. No key needed. {ref} is a published diagram's ID (never its key) or a share link's token, with @{revision} for one version; without it, the latest. A published diagram's answer has its title, description, madePublicAt, scene and kept image; a share link's has only id, access, the version shown and its date, latest, and every version's number and date, never anything from the scene. Images are the ones kept when each version was saved. An exact version's image is served with Cache-Control: public, max-age=31536000, immutable; one that follows the latest, and every JSON answer, with public, max-age=60. A share link's answers carry private instead of public: the visitor's own browser may keep them, but no shared cache may, so a revoked link stops for new viewers. Images carry an ETag of the version's chain hash (its content hash while it has none); If-None-Match with it answers 304. A private, deleted or unknown diagram, and an unknown or revoked token, answer the same 404, so the answer doesn't reveal which exist. Making a diagram private stops its links by ID at once, revoking a share link stops that link, and deleting the diagram stops both; copies already fetched stay with whoever has them.