A 3-year-old boy who died Monday was the fourth person to succumb to injuries from a massive explosion of fireworks on New Year’s Eve at a Honolulu home, and a doctor said six others faced long recoveries in Arizona, where they were sent to be treated for severe burns. The Honolulu medical examiner identified the toddler as Cassius Ramos-Benigno. After the disaster, Hawaii’s leaders intensified their oft-repeated calls to crack down on the state’s vast illegal fireworks trade with stepped-up enforcement and greater penalties.