-- 0095_tracks_emptied_at.up.sql — a slot the duplicate resolver emptied
-- waits for a copy fetched again (Scribe milestone #498).
--
-- When the resolver removes a file filed under another song's title and the
-- album holds no copy of that song as long as the song is, the row is marked
-- missing and stamped here with the same time. Missing-pair folding then pairs
-- it by title only with a track added after that time, a copy fetched again,
-- and not with one already on the album: on 2026-10-20 an emptied "Open the
-- Gateway" was folded into a file tagged so that holds another song.
--
-- The stamp counts only while it equals missing_since: a row whose file came
-- back and later went missing again is an ordinary missing row.
ALTER TABLE tracks ADD COLUMN emptied_at timestamptz;