Hindu traditions do not have one universally accepted deity whose sole role is palmistry. Palm reading is usually discussed as part of broader traditions of knowledge, astrology, bodily signs, and auspicious interpretation.
Ganesha may be invoked because he is associated with beginnings, wisdom, and removing obstacles. Saraswati may be connected through learning and knowledge. Brihaspati, associated with Jupiter and wisdom, may appear in astrology-adjacent contexts.
So the honest answer is not a neat name. It is a constellation of associations, which is very on-brand for a subject that already invited the planets to live on the palm.
