ArchiveSummary struct with archive metadata.
Example:
auto arc = Archive.open("/backups", "myarchive", "dar", readOpts().toLow());
auto s = arc.summary;
writefln("Size: %d bytes", s.archiveSize);
writefln("Compression: %s", s.compressionAlgo);
writefln("Cipher: %s", s.cipher);Summary metadata accessor with lazy caching.
On first access, the summary is fetched from libdar and cached. Subsequent accesses return the cached value without additional FFI calls. Use refreshSummary() to force a re-fetch from the underlying archive.