Function best_binary_codec 

pub fn best_binary_codec() -> u8

Returns the best available codec for binary content classes (structured binary — ELF, Mach-O, PE, object files, etc.).

LZ4 is the right choice in the current registry: ruzstd’s encoder is level-1-only and produces output roughly the size of the input, so ZSTD effectively means “store with extra overhead”. LZ4 gives 1.5–2× on structured binary at multiple-GB/s encode speed.

Will switch back to ZSTD once omnizip-zstd ships a real encoder (Phase C, tracked in omnizip/omnizip-rs).