The user-triggered "get full history" (backfill_channel_now) capped at
max_pages=60 = 3000 videos. A channel just over that (BBC Earth: 3403
uploads = 69 pages) stopped one page short, so its tail dribbled in over
the scheduler's paced 10-minute ticks (250 videos/tick) and the button
spinner looked stuck for ~18 minutes with no visible progress.
- Raise the immediate cap to max_pages=400 (20 000 videos) so any
realistic channel completes in the single background run.
- Make a high cap safe: backfill_channel_deep now re-checks the shared
quota before each page and yields at the backfill reserve (previously
quota was checked once by the caller before the whole run), and commits
the advanced cursor after every page so a restart resumes instead of
re-fetching — and re-charging quota for — pages already stored.
- Channel page: while loading, the button shows the live stored/total
count and a tooltip explaining the tail finishes in the background, so a
very large channel's paced remainder reads as progress, not a hang.
Adds deep-backfill paging tests (per-page cursor commit + resume, and the
per-page quota yield).
peter
e3ee1baa94