- The execution context is a lot more structured: Instead of a magic stack of arbitrary objects there are static objects for pages, stacks and paragraphs
- Page softness/keeping mechanic is now a lot simpler than before
- Only add line spacing between lines. Previously, line spacing was added below
every line, making `#box[word]` higher than just `word`.
- Compute box height of text as `ascender - descender` so that the full word is
contained in the box.