nx_ik.nx

nx_ik.nx -- CCD INVERSE KINEMATICS on nx_skeleton (Elara bar E5: "grab a wrist, the arm follows"; the same solver = robot-arm reach, per the reuse law). Cyclic Coordinate Descent: per sweep, each bone in the chain nudges its yaw/elevation by a fixed integer step in the direction that closes the effector->target angle -- signs come from CROSS PRODUCTS (no arctangent, no float), so the whole solve is integer-deterministic. Yaw sign law: +yaw rotates +x toward -z (CW in the XZ plane seen from +y), so yaw -= sign(crossY)*step. Elevation sign law: es = ty*|eff_h| - effy*|t_h| (elevation-angle comparison without division). license_tier: ORIGINAL