When it opened in 1990, Tribeca Grill must have seemed edgy and bold, a risky investment in a still-developing part of town. These days, it’s more about the comfort zone than the cutting edge, popular with lunching businessfolk and out-of-towners hoping to catch a glimpse of co-owner Robert De Niro. The warehouse-sized room has brick walls, big art by the late Robert De Niro Sr., and a mahogany bar in the middle. The food is straight-up New American; the wine list is highly regarded; and the loading dock is a lovely spot in warm weather.