NEW DELHI — Once bitter foes, India and Israel plan to strengthen their defense, intelligence and trade ties when Ariel Sharon attends a summit here today in the first official visit by an Israeli prime minister. Although Indian Prime Minister Atal Behari Vajpayee and Sharon are expected to sign a joint declaration on drug trafficking, the environment and other issues, the most significant deals are likely to be negotiated behind the scenes. Flush from a booming economy, India has gone on an arms-buying spree and wants to purchase advanced systems from Israel. At the top of the shopping list is...