Function classify_range_record 

pub fn classify_range_record(
    position: &RangeStreamPosition,
    record: &ChangeRecord,
) -> RangeStreamDecision

Route a single record relative to a range’s resume position. Routing order: other-range first (cheapest, most common), then already-applied, then the authority fence — so a record we have already applied is skipped without being treated as a fence violation, while a fresh stale-owner write is rejected.