The sum of the absolute maximum and absolute minimum values of the function \( f(x) = \tan^{-1}(\sin x - \cos x) \) in the interval \( [0, \pi] \) is:
\( 0 \)
\( \tan^{-1}\!\left(\dfrac{1}{\sqrt{2}}\right) - \dfrac{\pi}{4} \)
\( \cos^{-1}\!\left(\dfrac{1}{\sqrt{3}}\right) - \dfrac{\pi}{4} \)
\( \dfrac{-\pi}{12} \)