Construct an AnonymousSessionError.
Error code from auth server or SDK validation (e.g., "metadata_too_large")
Optionalmessage: string
Human-readable error message; defaults to generic message
Optionaldescription: string
Server's error_description field (optional)
Optionalcause: unknown
Raw error body or underlying cause (optional)
Error class for anonymous session operations. Maps authorization server error codes to SDK errors; distinguishes recoverable (silent recovery) from non-recoverable (throw to caller).