fix(openai): map system prompts to top-level instructions for ChatGPT auth requests

test/test.openai-auth.node.ts

@@ -199,15 +199,21 @@ tap.test('getModel uses ChatGPT Codex backend for OpenAI ChatGPT auth', async ()
   };
 
   try {
-    await model.doGenerate({
-      prompt: [{ role: 'user', content: [{ type: 'text', text: 'hello' }] }],
-      inputFormat: 'prompt',
-    } as any);
+    await smartai.generateText({
+      model,
+      system: 'system prompt',
+      prompt: 'hello',
+    });
 
     expect(capturedRequest?.url).toEqual('https://chatgpt.com/backend-api/codex/responses');
     expect(getHeader(capturedRequest?.init, 'authorization')).toEqual(`Bearer ${tokenData.accessToken}`);
     expect(getHeader(capturedRequest?.init, 'chatgpt-account-id')).toEqual('workspace-1');
     expect(getHeader(capturedRequest?.init, 'originator')).toEqual('smartai');
+    const capturedBody = JSON.parse(String(capturedRequest?.init?.body));
+    expect(capturedBody.instructions).toEqual('system prompt');
+    expect(capturedBody.input).toEqual([
+      { role: 'user', content: [{ type: 'input_text', text: 'hello' }] },
+    ]);
   } finally {
     globalThis.fetch = originalFetch;
   }