fix(macos): restore directory deferral lost in the AppleDouble extractor

[thcp]

Fixes #508. Follow-up to #506 -- a regression introduced by that PR.

#506 replaced Archive::unpack with a per-entry unpack_in loop so AppleDouble ._ members could be skipped. The loop reproduced the iteration but not the two things unpack does around it.

1. Directory deferral

Archive::_unpack (tar-0.4.45 archive.rs:245-265):

// Delay any directory entries until the end (they will be created if needed by
// descendants), to ensure that directory permissions do not interfere with
// descendant extraction.
directories.sort_by(|a, b| b.path_bytes().cmp(&a.path_bytes()));

A directory carries its own mode. Created inline in archive order, a 0o555 member exists before its contents are written, and the next file inside it fails File::create with EACCES -- unpack_without_apple_double returns Err and first-run setup dies with no fallback. ditto and tar both record such modes faithfully, so this was reachable, not theoretical.

Deferring costs nothing on a streaming archive: directory entries carry no data, so the second pass applies metadata only.

2. destination canonicalization

Restored before the loop. On Windows this supplies the \\?\ extended-length prefix so member paths over 260 characters still extract.

Not affected: traversal protection

unpack_in rejects ParentDir components, strips RootDir/Prefix, and calls validate_inside_dst -- which canonicalizes on every entry -- so zip-slip, absolute members and symlink escapes were blocked throughout. This was a robustness regression, not a security one.

Impact

Latent on shipped artifacts. The published 0.16.0 pack has no restrictive directory members: extracting it end to end produced 27,797 files and 0 sidecars. Windows takes the zip path for updates, so the long-path loss was theoretical there. Fixed because the next pack is not guaranteed to be as forgiving.

Verification

New test extract_tar_archive_survives_a_read_only_directory_member builds a .tar.zst whose 0o555 directory member precedes its file member -- the order that broke -- and asserts the file extracts and the directory keeps its archived mode.

Confirmed the test is not vacuous: with directories created inline it fails; with deferral it passes.

cargo fmt --check   OK
cargo clippy        0 errors
cargo test          59 passed, 0 failed