If \( I(x) =\displaystyle \int e^{\sin^2 x}\,(\cos x \sin 2x - \sin x)\,dx \) and \( I(0) = 1 \), then \( I\!\left(\dfrac{\pi}{3}\right) \) is equal to:
\( -\dfrac{1}{2}\,e^{\dfrac{3}{4}} \)
\( \dfrac{1}{2}\,e^{\dfrac{3}{4}} \)
\( -e^{\dfrac{3}{4}} \)
\( e^{\dfrac{3}{4}} \)