Explain the problem.
Starting with pandoc 3.8, smart quotes do no longer honor the 'lang' specifcation when creating pdf via '--pdf-engine typst'. It did work till 3.7.0.2, starting with 3.8 up to the latest (3.8.2.1) it does not anymore.

test.md:

---
lang: de-CH
papersize: a4
---

# Titel
Ein "Text" mit Quotes.

pandoc-3702 -s -o test.pdf test.md --pdf-engine typst creates a pdf with nice & correct quotes: Ein «Text» mit Quotes
pandoc-3821 -s -o test.pdf test.md --pdf-engine typst creates a pdf with nice but english quotes: Ein “Text” mit Quotes.

Interestingly, when creating an intermediate .typ file pandoc-3xxx -s -o test.typ test.md followed by typst compile test.typ, both version result in nice & correct quotes: Ein «Text» mit Quotes. Although the .typ files differ quite a bit between these pandoc versions, the result after typst compile is identical.

Pandoc version?
3.8.2.1 vs 3.7.0.2 with typst 0.13.1