Consider the voyage of the container ship Melina, which set sail Wednesday from a Chinese port near Shenzhen with products bound for U.S. households, a hulking symbol of how the flow of goods is adapting in a global economy crippled by a pandemic. Capable of carrying almost 4,300 containers, she’s downright petite in an industry where the biggest can handle more than 20,000. The Melina is part of a budding fleet of smaller vessels that Covid-19 has thrust into service between the world’s biggest economies. Smaller means faster. She’ll dock in Los Angeles on July 6 after a 12-day nonstop journey — a week ahead of a larger ship doing the same route.