push rejected ticks that went backwards across buckets but absorbed any
tick whose timestamp fell inside the open bucket — including one older
than the last tick already absorbed. Such a stale tick silently
overwrote the bar's close with an outdated price.
Track last_ts on OpenBar (set in from_tick, advanced in absorb) and, on
the same-bucket path, reject a tick whose timestamp predates it with
Error::Malformed, leaving the open bar untouched. Ticks that share a
timestamp are still accepted, since several trades can land in the same
millisecond.
kingchenc
2cebb3cca1