Library > Releases (and All) "Date added" was position-based: every source
got a rank of index / len and the merge interleaved sources by that
relative rank, so a purchase from yesterday could sit behind favourites
from months ago. The favourites API carries favorited_at (never modelled)
and purchases purchased_at; local favourites keep their own stamp. Rows now
carry addedAt, the merge and release-sort.js order by it newest first, and
only undated rows fall back to the rank, always after the dated ones.
The playlist view's Default and Date added never sorted: they reversed
whatever order the rows were in (after a Title sort, a reversed title
order), which is why flipping the direction took two clicks and switching
fields kept the old order (#782). Rows now carry their loaded position —
Qobuz's insertion order is its added order — Default and Date added sort
by it, and the direction toggle reverses a canonical order.
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