[JS] abortSignal does not work with dotprompt

[chrisvariety]

Describe the bug
When combining dotprompt (ai.prompt) with abortSignal, an error is thrown:

TypeError [ERR_INVALID_THIS]: Value of "this" must be of type EventTarget
    at Object.addEventListener (node:internal/event_target:596:13)
    at buildFetchOptions (/Users/chrismcc/workspace/lexikon/node_modules/@google/generative-ai/dist/index.js:450:15)
    at constructModelRequest (/Users/chrismcc/workspace/lexikon/node_modules/@google/generative-ai/dist/index.js:385:55)
    at makeModelRequest (/Users/chrismcc/workspace/lexikon/node_modules/@google/generative-ai/dist/index.js:391:41)
    at generateContent (/Users/chrismcc/workspace/lexikon/node_modules/@google/generative-ai/dist/index.js:868:28)
    at /Users/chrismcc/workspace/lexikon/node_modules/@google/generative-ai/dist/index.js:1188:25
    at async ChatSession.sendMessage (/Users/chrismcc/workspace/lexikon/node_modules/@google/generative-ai/dist/index.js:1211:9)
    at async callGemini (/Users/chrismcc/workspace/lexikon/node_modules/@genkit-ai/googleai/lib/gemini.js:1103:26)
    at async /Users/chrismcc/workspace/lexikon/node_modules/@genkit-ai/googleai/lib/gemini.js:1149:11
    at async /Users/chrismcc/workspace/lexikon/node_modules/@genkit-ai/core/lib/action.js:244:14 {
  code: 'ERR_INVALID_THIS',
  traceId: '40bd7c4a75cb583503c9026df4376d04',
  ignoreFailedSpan: true
}

To Reproduce

Very simple reproduction:

import { googleAI } from '@genkit-ai/googleai';
import { genkit } from 'genkit';

const ai = genkit({
  plugins: [googleAI()]
});

const testPrompt = ai.prompt('test');

const main = async () => {
  const { text } = await testPrompt(
    {},
    { abortSignal: AbortSignal.timeout(1000) }
  );

  console.log(text);
};

main().catch(console.error);

My test.prompt file in a prompts directory:

---
model: googleai/gemini-2.5-flash
---

This is a test prompt.

Expected behavior
abortSignal would be passed correctly without error.

Screenshots
n/a

Runtime (please complete the following information):

• OS: MacOS
• Version Sequoia 15.5

** Node version
v22.14.0

(also reproduces on v24.4.1)

Additional context
Maybe related to #3268