Let \( f:\left[-\frac{\pi}{4},\frac{\pi}{4}\right]\to \mathbb{R} \) be defined as If \( f \) is continuous at \( x=0 \), then the value of \( 6a+b^{2} \) is equal to:
\( e \)
\( 1-e \)
\( 1+e \)
\( e-1 \)