Function known_max_input_sequence 

pub(crate) fn known_max_input_sequence<'a>(
    inputs: impl IntoIterator<Item = &'a FileMeta>,
) -> Option<NonZeroU64>

Folds file-level sequence bounds into the output sequence bound of a merge.

A bound can be a row maximum or an admission marker; compaction must preserve both for sequence-based pruning. Unknown bounds must remain unknown rather than being replaced with a partial maximum.