Triangle $ABC$ has $\angle BAC=60^{\circ }$, $\angle CBA\le 90^{\circ }$, and $AC\ge AB$. Let $H,I,O$ be the orthocenter, incenter, and circumcenter of $△ABC$, respectively. Assume that the area of pentagon $BCOIH$ is the maximum possible. What is the ratio $OI/R$, where $R$ is the circumradius of $△ABC$?