Relative to an origin \(O\), the points \(A, B, C\) have position vectors
\(\mathbf{i}, \quad \mathbf{j}+\mathbf{k}, \quad \mathbf{i}+\mathbf{j}+\theta \mathbf{k}\),
respectively. The shortest distance between the lines \(A B\) and \(O C\) is \(\frac{1}{\sqrt{2}}\). Find the value of \(\theta\).