Report inverse-kinematics residuals at the returned configuration

[Afloat16]

The inverse-kinematics loop measures the residual before applying an update. At the iteration limit, it can return an updated configuration with the preceding residual and success flag. Recompute the same weighted position/quaternion norm at the returned configuration so the diagnostic and convergence classification describe the actual result.

Preserves the solver, damping, progress termination, iteration count and inplace/copy behavior. Adds seven regression methods covering last-step translation, rotation and combined-pose convergence, clipped and regularized updates, an already converged pose and progress termination. The position and planar-angle references are computed independently from the final pose.

Validation: all 37 original inverse-kinematics cases pass in both versions. The same seven new methods give 5 failures before the repair and seven passes afterward. Generated the bindings from the unchanged canonical autowrap with genuine MuJoCo 3.15.0 headers; the tracked functions.py remains unchanged.

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