EXCLUSIVE NEW TO MARKET WAVE HILL AREA  Renovated & Spacious 7-Bd. House with Patio & Level, Grassy Yard on Private Cul-de-Sac    Scenically situated on a private cul-de-sac alongside a stream with two footbridges, this renovated 7-bedroom, 6.5-bath house was built in 1940. It enjoys an inviting rear dining patio and level, grassy back and side yards.    Standout features include: an entry vestibule; center hall; living room with wood-burning fireplace and French doors to the patio and yard; formal dining room; spacious center-island eat-in kitchen with quartz countertops, 3 sinks and stainless-steel appliances (2 Sub-Zero refrigerators, 6-burner Thermador stove, Bosch oven and 2 dishwashers); family room; den (which could be used as a 1st-floor guest room with full bathroom); master bedroom suite (with private roof deck and windowed dressing area with 3 closets, including 1 walk-in); master bathroom with whirlpool tub and radiant-heat floor; finished walk-out basement with recreation room, large private office and half bathroom; 2-zone central air-conditioning; 2 separate multicar driveways; attached 1-car garage; 100-by-110-ft. corner lot.    Conveniently located for well-known private schools (Riverdale Country School and SAR Academy), Wave Hill public gardens and culture center and the Metro-North trains to Manhattan.