Media files not Pulled from Origin Site

When copying over a post that has media in the post, a thumbnail attached, or has meta with an attachment ID the original image does not come over with the post. This means that crops cannot be changed and the media is permanently attached to the origin site and could go away if deleted on the origin site - even if it's still used on the cloned-to site.

Sideloading the file into the cloned-to site (preferrably with an action or filter to allow us to specify files used in metadata) would be very useful.

The issue names no files, tests, or entry points. Start by tracing the repository's post-copy flow for embedded media, thumbnails, and attachment IDs; done means copied posts have local media and metadata attachments can be handled through an action or filter.

Written by the indexing model from the issue text.