Let A, B, C be three points in the xy-plane, whose position vectors are given by
\[
\sqrt{3} \hat{i} + \hat{j}, \quad \hat{i} + \sqrt{3} \hat{j}, \quad \text{and} \quad a\hat{i} + (1-a) \hat{j}
\]
respectively with respect to the origin \( O \).
If the distance of the point \( C \) from the line bisecting the angle between the vectors
\( \overrightarrow{OA} \) and \( \overrightarrow{OB} \) is \( \frac{9}{\sqrt{2}} \), then the sum of all possible values of \( a \) is: