🦿 Prosthetic Knee Swing Phase: Damped Double Pendulum, Toe Clearance and Heel-Strike Extension

An above-knee prosthesis swings under a driven hip while the shank hangs on a damped, spring-assisted knee. Tune the damper and see peak knee flexion, toe clearance against the floor and the terminal extension impact, with an RK4 solution checked against pendulum theory.