If the prompt is about state building, is that governance? Are we allowed to talk about how the state governs itself/ consolidates/ legitimizes its power, or are we only allowed to talk about state expansion?
Yes - state building is one form of governance (how a place governs)
You can reference all aspects of government in the “state building” theme.
Also, make sure you look how the documents approach “state building” to see where you want to take it in the essay. You may look at writing about governance in a time period more generally as contextualization then narrow the focus for your thesis.