An estimate, not an exact figure — used only to decide whether to break before starting the table (wrapping within cells / the real style is only known once AutoTable draws); a table longer than a page already paginates itself within AutoTable, so the engine doesn't need to know the real height.
draw onto the doc; must not compute page-breaks itself — use ctx.ensureSpace
The shared contract for every block — it must answer two things: how tall, and how to draw. text/image/table/group/report all implement this same interface.