🎯 Long-Range Projectile Lab - 2D Trajectory Profile, Mach Map and Drag Curve

2D companion of the Long-Range Projectile Lab: a side-view trajectory coloured by Mach number, the vacuum parabola for comparison, the generic drag curve Cd(M) with a moving operating point, top-view wind and spin drift, and an elevation sweep, using the same RK4 physics module as the 3D page.