The like count only watched bookmark lists by #a, so when someone removed
an event their new (replaceable) list no longer matched the filter and
never arrived — the count stayed stale until reload. Also watch known
likers by `authors` and track each author's current liked-coords, diffing
prev vs next on every update so a dropped coord decrements live. Verified
end-to-end against a relay: a like incremented the count and the same
key's updated list (coord dropped) decremented it with no reload.
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
