The pilot/owner/builder reported that at 30 to 50 feet above the runway in a steep climb after takeoff, the engine stopped producing power. The airplane "nosed over quickly" and landed hard on the nose wheel, bounced, and landed hard on the nose wheel again, collapsing it, and causing substantial damage to the firewall and airframe. Examination of the airplane's engine by an FAA airworthiness inspector revealed that both magnetos were improperly grounded at installation. The installation as found resulted in a degraded performance, and over time, resulted in a complete ignition failure and total loss of engine power.