Export `representative` from records.ts: the album's copy of a file that
its record is read from. `store.getFileByID` now returns that copy, so
`download()` writes under the date `photo.savePath` names. `lib.backup()`
takes each file's copy by the same rule from all of its albums, and every
album links that one path. Tests cover one file in two albums whose copies
carry different edited dates, for `download()` and for `lib.backup()`.
Model: opus-5-5
sneak
8992c7c5a9