TODO: consider dom sandbox for testing ui (see long desc)

see https://discord.com/channels/1388415325036609617/1458088018232479824/1484195713347879012

cmd/pkgserver/ui/static/test.ts

@@ -271,7 +271,7 @@ interface GoNode {
 export class GoTestReporter implements Reporter {
     // Convert a test tree into the one expected by the Go code.
     static serialize(node: TestTree): GoNode {
-        if (!("children" in node)) return { name: node.name, subtests: null };
+        if (!("children" in node)) return { name: node.name };
         return {
             name: node.name,
             subtests: node.children.map(GoTestReporter.serialize),