Every error code and whether retrying can help

The registry every RFC 9457 problem document from trooth.co draws on: each code with its status, fixed title, retryable flag, next action, and terminal (true when repeating the same request cannot change the answer, exactly not retryable). A code keeps its meaning once published. Cached for one hour. Readable cross-origin: the response carries Access-Control-Allow-Origin: * and never Access-Control-Allow-Credentials, so a browser on any site may read it without cookies.