fix(typst): prevent breaking inside definition items

[mcanouil]

Ensure terms and their descriptions remain together by preventing breaks within definition items.

The rule needs to be separate from the content rule, because here we play on the implicit block generated by Typst.

As this is a visual change, there are no tests, but I believe non breaking term/definition is a sensible default.

Code	Before	After
--- title: "Quarto Playground" format: typst keep-typ: true --- ## Introduction {{< lipsum 4 >}} Multi-format output : Generate HTML, PDF, Word, ePub, and more from one source.

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[gordonwoodhull]

I added a test using ensurePdfTextPositions. Without the fix, it reports

Cannot compare positions: "Generate HTML" is on page 2, "Multi-format" is on page 1    

[mcanouil]

Wow, is this ensurePdfTextPositions new?

[gordonwoodhull]

Yes, I added these to validate article layout in Typst PDF output.

It's currently just right-of, above, etc, and per-side alignment, so I tested that they are not left-aligned, but the predicates only work if the items are on the same page, so it worked out handy for this.

Come to think of it, I think I could have tested that the left edge is to the right of the other left edge as a positive test. 🤔

I'm still getting used to it and figuring out the complete API, please try it out and see if it's helpful. I'll add dev-docs soon.

In theory it should also work with LaTeX tagged PDFs, but I haven't tested that yet.