Prelude bytes + offset math for the fixed two-entry (Finder Info +
resource fork) container, so a consumer serving a virtual sidecar
(fsinspect's FUSE AppleDouble mode) can answer getattr from total_len
and dispatch range reads via plan_read without materializing the
container. Byte-equivalence with build_appledouble is pinned by test.
Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
The codec module (src/appledouble.rs) lifted verbatim from ad-decoder's
working tree at extraction time — including its uncommitted entry-ID
constant additions — with only the crate-level docs rewritten. 17
in-module tests carried over and green.
Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
