A watched video the catalog did not know at import time waits in `takeout_items`. The Shorts job now
settles those rows right after its probe (the only place a video's Short-ness becomes known), every
user's, a commit each: `reader.takeout.apply_waiting`, its count in the job's result.
`GET /api/takeout` is what the settings page reads: the user's last import run (`jobruns.last_run`)
and the kept videos by kind and outcome, "waiting" for one not known yet.
The YouTube API reads neither a user's watch history nor their Watch later list, so the Takeout
export is the only way in. `POST /api/takeout` takes one file of it (watch-history.json or
Watch later-videos.csv, told apart by content), keeps its videos in `takeout_items` and queues the
user's `takeout_import` run, whose outcome reaches their inbox.
The run marks watched the known videos the Shorts probe has cleared, at the Takeout time; a Short
is not marked, and a state the user set here (watched, hidden, or changed after that time) wins, by
the upsert's own condition. A video the catalog does not know yet waits with no outcome. Watch later
videos are fetched if unknown and appended oldest first.
An ad-hoc run can now ask for a completion notice (`run_ad_hoc(..., notify=True)`).
peter