Paused sandboxes started from a custom image survive the loss of their host

A paused sandbox started from your own image is no longer stopped when its host is lost, as long as its saved copy is complete and another host holds the image. Its next wake restores it from that copy on a host that holds the image. While no such host can take it, a wake returns 503 no_capacity with the detail that it starts from its saved copy as soon as one has room. If the image is deleted or rebuilt, or no other host holds it, the sandbox is stopped as before, and its parked charge ends when its host was lost.