YT-28433: Fix slot-fill race in AnyN future combiner

TAnyNFutureCombiner materialized its result when the responder drawing
responseIndex == N_ - 1 completed. That index reflects reservation order
(ResponseCount_++), not write-completion order, so the triggering responder
could call VectorFromThis() while a lower-indexed responder had reserved but
not yet filled its slot, tripping YT_VERIFY(opt.has_value()). Trigger on a
separate FilledCount_ counter incremented after the slot is written so all
writes are complete and visible.
commit_hash:73e805c27dbcbeeda29e81d353a03d411d99ccd3

0 files changed, 0 insertions, 0 deletions