PreparedEdit::page_protected and Notebook::save_unlocked publish a page-model
edit under the section key. The page writer runs unchanged on a plaintext twin
of the unlocked section (every labelled revision and payload under its own
identity); the revisions the twin gained are squashed onto the real file with
objects sealed under fresh IVs and payloads under the file IV.

OneNote 2010 unlocks and reads the result and keeps editing it
(corpus/protected-edit). Its follow-up revisions showed that a revision with a
dependency carries no key node; the reader accepts that and the writer matches.

Assisted-by: claude-fable-5.1