An innocuous WhatsApp “Hi” could end up transforming a $1 trillion industry. Facebook Inc. bought its way into India’s internet commerce sphere last week with a $5.7 billion investment in Reliance Industries Ltd., a sprawling conglomerate in everything from telecom to energy. They launched their first pilot within days, a program covering three Mumbai neighborhoods where consumers can send that monosyllabic greeting to a designated number, bringing up an in-chat interface through which they then browse a catalog of goods on Reliance’s Jiomart, place an order and arrange for pickup.