Editing a journal entry overwrites the saved entry

I had a whole journal entry with a bunch of images that I spent hours slowly adding to, and right before publishing it, I edited one of my previous entries and all my progress was gone. I realised it was because the entry content gets saved to localStorage, but if you edit an entry, it gets overwritten.

Start by tracing the journal entry editor and its localStorage persistence, focusing on what happens when an earlier entry is edited. Reproduce the loss with an unpublished entry containing images; done means editing a saved entry no longer removes the current unpublished progress.

Written by the indexing model from the issue text.