Behind a townhouse on the East Side sits a square of lawn no bigger than a rug, and in October the light comes off the river low enough to gild it. McNelly Lawn Care and Landscaping keeps squares like that one honest — cutting, trimming, edging clean against fence and flagstone, hauling leaves out before they mat down over the grass. Small spaces show every mistake, which is precisely why they repay a steady hand. Come spring the cleanup starts the cycle over and the yard comes back. Manhattan and the neighborhoods around it.