Pawtucket's triple-deckers stand shoulder to shoulder, and the strip of lawn out front of each one is the whole yard — a green rug the width of a porch. GreenDream Landscaping & Services takes those small squares seriously: mowing, trimming, edging and cleanups, the routine that keeps a dooryard looking tended instead of tolerated. Evening is the good hour on these streets, when the light goes copper on the clapboards and somebody waters a tomato plant on the steps. A neat lawn on a dense block is a kindness that multiplies fast — one tidy yard makes the next one want to keep up. That's the pleasure of the work in a city built this close together.