Constant PACK_FLAG_LZ4 

pub const PACK_FLAG_LZ4: u32 = _; // 1u32

Bit flag — at least one entry in this pack uses LZ4 compression. Diagnostics-only: per-entry compression is decided by AssetSource::Packed.compression. The flag is set when the writer applied LZ4 to any entry, so a quick header scan can tell whether the pack as a whole is mostly compressed.