Each list-v2 page is sorted on its own, so fetchMoreFolderContents'
col.items.concat(items) didn't keep the column sorted once a second
page came in — a naive concat leaves the new page's items after the
old ones regardless of the active sort column. Extracts the merge
comparator from formatFolderItemsV2 into a shared sortStorageItems
helper and re-sorts the combined list after every load-more.
Ivan Vasilov
dedbea2ed3