Callouts that nest, and tables that look like tables

GitHub-style callouts were already rendering. Real documents asked for more: a callout inside a callout, a table inside that, a task list inside the inner one, and a fold you can actually see.

Fold, nest, and keep going

A + after the callout type starts it open. A - starts it closed. The summary is the first line, and a chevron on the summary turns when you open it.

> [!info]+ Project status
> Here is where things stand.
>
> > [!warning]- Blockers
> > - [ ] Waiting on review
> > - [x] Assets delivered

Nested callouts keep their own type and their own fold. Tables and task lists inside them stay inside them. The reading-position shortcuts stop on a callout as its own block, including one nested in a list or inside another callout, so j/k does not skip the whole thing.

Tables

Tables in the document body pick up the reading styles now: borders, spacing, and a header row that looks like a header. A table inside a callout uses the same treatment, so a status table does not fall back to raw browser defaults in the middle of a note.