Insert oil rig here? When most people think of Costa Rica, they don't imagine oil rigs stationed off the pristine beaches. Nor do they envision pit mines cutting into the cloud-forested mountains. But, despite the country's noteworthy conservation efforts, its scenic vistas and extraordinary biodiversity face ongoing threats from extractive industries -- and from international trade deals. Nearly two years ago, Costa Rican nationals and admirers thought they'd been given reason to rest easy. In May 2002, responding to a large-scale mobilization of the country's environmentalists, President Abel Pacheco announced a moratorium on oil exploration and open-pit mining in Costa …