Function read_file_bytes_for_pack 

pub fn read_file_bytes_for_pack(path: &Path) -> Result<Bytes>

Read a pack file as zero-copy Bytes. For packs that clear the mmap threshold, the underlying memory is the mmap’d region — every Bytes::slice into it is a zero-copy view. Smaller packs fall back to a heap read wrapped in Bytes. Public because the pack reader lives in a sibling module and needs to bypass the pub(super) gate on read_file_bytes.