“Well, I’m a physicist.” “He’s a physicist too,” she chimed in. She couldn’t help bragging about her brilliant boyfriend. “Oh, all right!” Emma’s dad responded as they engaged into some deeper conversation about physics, until they heard… “Dinner is ready!” or until they heard-- "Dinner is ready!" Thanks.
neither... a comma and that line of dialog moved up into the same paragraph is the correct way... however, that overlong dialog tag makes no sense, since the dad couldn't be saying, 'oh, all right!' the whole time 'they' conversed, could he?... keep in mind that 'as' means 'at the same time as' and don't use it to tie two actions together that can't possibly be done concurrently... here's one way it could be done, to have it make sense: btw, 'engaged into' is also incorrect... the term is 'engaged in'...
