A handful of photos is the whole ~5 MB quota, and past it the document
stopped saving. The autosaved JSON now keeps an `idb:<key>` per picture
and the bytes live in their own store; the key is a sampled content
hash, so a picture used twice is stored once and each save sweeps what
the document no longer names.
loadDocument is async as a result and Editor.svelte awaits it. Where
IndexedDB is unavailable the data-URIs stay inline exactly as before.
Steffen Becker
6a313e5692