Decouple introspection and update

[andreasKroepelin]

By @laurmaedje on Discord:

What I'm referring to specifically is to change this

locate(loc => {
  repetitions.update(rep => calc.max(rep, pause-counter.at(loc).first() + 1))
})

to this

locate(loc => {
  let c = pause-counter.at(loc).first()
  repetitions.update(rep => calc.max(rep, c + 1))
})

referring to this: https://github.com/typst/packages/blob/98677b0833970b0b08f77e456cdd14aee7e10768/packages/preview/polylux/0.3.1/logic.typ#L252