Artifacts in cloud sessions give a clearer message when access is refused

In a cloud session, if Claude Code is refused (an HTTP 403 error) when it fetches the organization's settings for artifacts, Claude now gets its own instruction. It is told not to retry now, and to tell you that artifacts are unavailable because Anthropic couldn't confirm your organization's settings for this cloud session, and that it isn't a problem with your network. Before, only a general message was given, and only for one other kind of failure.