Fix undefined bug

test/fixtures/bash-test.ts

@@ -14,7 +14,6 @@ import type { Payload } from "../../external.ts";
  */
 export default {
   "~pullfrog": true,
-  agent: null,
   prompt: `Create a file called test-runner.js with the following content:
 
 \`\`\`javascript

test/fixtures/basic.ts

@@ -2,7 +2,6 @@ import type { Payload } from "../../external.ts";
 
 export default {
   "~pullfrog": true,
-  agent: null,
   prompt:
     "List all files in the current directory, then create a file called dynamic-test.txt with the content 'This was loaded from a TypeScript file!', then delete it.",
   event: {