Your answer would be Dialogue :)
The words in the brackets are telling the actors what to physically do, meaning it would be a stage direction.
It isn't dialogue because that is a conversation between two people.
It isn't dialect because that is how a person speaks. There is no speaking in the brackets.
It isn't narration because it isn't spoken allowed for the audience.
It isn't a description because that is too broad a term more often used for emotions.
The first one is the correct way to use it, since it separates the parts of the sentence into fragments that can still be understood without changing the meaning of the entire sentence.
