So from this, I gather Finnish doesn't invert the subject and verb for question sentences. How do they indicate this then aside from context (since kuka here indicates a question)?
No, the word order stays the same. Or well, you can, of course, change it too, but then there's always a slight change in nuance/tone as well.
If you form a yes/no question with the question suffix -kO, whichever word gets the suffix comes first. Usually, for a neutral question, it's the verb.
Hän on lapsi. - She is a child.
Kuka hän on? - Who is she?
Missä hän on? - Where is he?
Miksi hän on täällä? - Why is he here?
Onko hän lapsi? - Is she a child?