Function stamped_merge 

pub fn stamped_merge(
    cur: StoreRange,
    writer_gen: u64,
    start: usize,
    count: usize,
) -> StoreRange

2026-09-25: Record a write of [start, start + count) by writer_gen. The same non-zero owner merges it with merge_interval; any other owner, or an unclaimed range, is replaced by the write. Merging across owners would leave another sequence’s rows inside the interval.

The same-owner case relies on merge_interval replacing on a gap, which merge_interval_replaces_on_a_gap pins.