Fix it, or let it go

When a post fails on one channel, the next step should be obvious. Before, it was an unlabelled X.

What's new

• The failed-publish banner's X is now a "Keep and edit" button. As before, it returns that channel to a draft you can fix and republish

• Trying to remove a failed channel opens a dialog first. It recommends keeping the channel and editing the post

• The dialog shows the error that came back from publishing, when there is one

• The channel is only deleted when you choose "Remove permanently" in that dialog, which warns that it cannot be undone

• If the delete does not go through, the dialog stays open so you can try again