Add Playwright tests for XB AI module

Possibly a follow up issue.

• There needs to be tests for nodes and we need more scenarios
• We need some other Agent Tests: https://www.drupal.org/project/ai_agents_test/issues/3537161

This provides a good foundation!! We can include additional tests for page builder tasks and other cases in a follow-up.

Follow-up issue created #3542219: Expand Playwright test coverage for XB AI module

Merged into 1.x! Not backporting because #3538439: Running tests locally is difficult to match with the CI wasn't backported.

This caused a regression on 1.x: it is a new flaky test.

I've now seen these new tests fail in multiple MRs, always like this:

  3) [webkit] › tests/src/Playwright/xbAi.spec.ts:127:7 › XB AI Features › Should verify AI panel API request and response payload 
    Error: expect(received).toBe(expected) // Object.is equality
    Expected: "1"
    Received: "2"
      153 |     expect(requestBody.messages[0].text).toBe(query);
      154 |     expect(requestBody.entity_type).toBe('xb_page');
    > 155 |     expect(requestBody.entity_id).toBe('1');
          |                                   ^
      156 |     expect(requestBody.selected_component).toBe('');
      157 |     expect(requestBody.layout).toBe('{}');
      158 |     expect(requestBody.active_component_uuid).toBe('');

— https://git.drupalcode.org/project/experience_builder/-/jobs/6274833#L1337

While it's still fresh in your head, please harden this 🙏

Also, many more failures from this new test coverage in https://git.drupalcode.org/project/experience_builder/-/jobs/6275720 (4 of the 6 failures!) — although maybe those failures are caused by the changes in that MR, although I really don't see how.

I'll re-test it (queued: https://git.drupalcode.org/project/experience_builder/-/jobs/6275778), but would very much appreciate you manually testing the AI functionality with that MR checked out. 🙏

Much appreciated, @NarendraR, @justafish and @jessebaker! 😊🙏

jvbrian I deleted my push because I accidentally created my test file in the wrong issue. Since I’m creating new Playwright tests, they should be in issue #3537161.