Function scan_shard_classified 

pub fn scan_shard_classified(
    content: &[u8],
    range_start: usize,
    range_end: usize,
) -> (ShardRecords, Vec<u8>, Option<usize>)

[scan_shard] plus a parallel per-record class column (see the PREPASS_CLASS_* codes). Same records, same handoff; the class byte lets the browser host extract pre-pass span lists (today: styled items) from the stitched shard columns WITHOUT waiting for the serial pre-pass scan.