ReadonlyendWorld position of the chain tip after solving. Equals the target when reachable.
ReadonlyjointWorld position of the middle joint (elbow, knee), on the pole side.
false when the target lay outside the chain's annulus and the pose was
clamped — end is then the closest the tip can get, not the target.
The pose produced by solveTwoBoneIK.
jointandendare stable object references that the solver writes into — the vectors are mutable, the fields are not reassigned — so a caller can hold one solution and reuse it every frame.