The container every OpenDocument file shares, moved from WordCraft
(crates/formats/src/odt/crypt.rs, odt/flat.rs, the package reading and
writing in odt/import.rs and odt/package.rs, crates/doc/src/zip_guard.rs
at 06c2ae6f) so that the ODT and ODS readers build on one copy.
- Package and PackageWriter: the ZIP with its mimetype and manifest,
within Limits (entries, bytes per file, bytes per package).
- Manifest: read by namespace whatever the prefix, as GridCraft's ODS
reader did; written as LibreOffice lays it out.
- crypt: AES-256-CBC with PBKDF2, read and written, with the per-file and
per-package key-derivation budgets.
- flat: a flat document to a package and back, for any media type (the
WordCraft code wrote the text one only).
- zip_guard: the entry-count check before zip parses a directory.
No document content is read here.
