cmd/pkgserver: set exit code when running JS tests from CLI

cmd/pkgserver/ui/static/test.ts

@@ -198,6 +198,10 @@ export class StreamReporter implements Reporter {
         this.#skips = [];
     }
 
+    succeeded(): boolean {
+        return this.#successes.length > 0 && this.#failures.length === 0;
+    }
+
     register(suites: TestGroup[]) {}
 
     update(path: string[], result: TestResult) {