Extra holds what the parser does not name (ADR-0002), and title, aliases, tags,
order, slug and draft are all deleted once lifted. date was the one exception,
so a template reading .Extra.date got the raw YAML value sitting beside the
parsed time — two spellings of the same fact, which is how they drift.
One line, and a test that names every lifted key rather than just this one, so
the next field added to Bundle has somewhere to fail if it forgets.
Latent item cleared. It had been waiting on "whatever next reads Extra
generically"; nothing does yet, but the fix was smaller than the row describing
it.