I still couldn't find the correct Razor syntax, but this worked to add the following JavaScript right after the Razor call:
.Render())…
<script type="text/javascript">
$.ig.loader(function () {
// Initially just show the Active records
$("#igGrid").igGridFiltering("filter", ([{ fieldName: "Active", expr: "True", cond: "true" }, ]));
});
</script>
}