Reuse unchanged IPA entries through the packing index and APFS clones,
and keep Mac app and derived-profile shader outputs while their inputs
match. Preserve main's shader regression checks and .NET discovery.
Count uncompressed bytes in streamed files so a size change aborts the
pack without replacing the previous IPA or index. Cover both deflated
and stored streams with growth and shrinkage regression tests, and
record the cause and fix in the packing reference.
Co-authored-by: Suraj Mandal <surajmandalcell@gmail.com>
