BUG (YB1): the auto-watch checkpoint marked a video watched once position
crossed `duration - FINISH_MARGIN` (10s). For clips shorter than ~10s that
threshold is negative, and for ~11-20s clips it's only a few seconds in, so the
5s checkpoint tick marked short videos watched almost immediately (clearing their
resume position). Cap the margin at half the clip: Math.min(FINISH_MARGIN, dur/2).
Cleanups (behavior-neutral):
- Extract format.formatDate(iso, lang) — the day/month/year toLocaleDateString
option object was duplicated verbatim in PlayerModal (fullDate) and VideoCard.
(ChannelPage's "joined" is month/year only, so it's left as-is.)
- The in-bar prev/next buttons now reuse goPrev/goNext instead of re-implementing
the step + bounds inline (they already exist for the side arrows + keyboard).
- Memoize savedPrefs so the ['me'] cache read + spread runs once, not on every
render (it only seeds the initial autoMode/loopMode state).
tsc green, knip clean, localdev boots healthy.
31c1284eb7