Add AI sources to order attribution data

[chihsuan]

All Submissions:

• Have you followed the Contributing guidelines?
• Does your code follow the WordPress' coding standards?
• Have you checked to ensure there aren't other open Pull Requests for the same update/change?

Changes proposed in this Pull Request:

Related to WOOA7S-206

Add AI platforms chatgpt.com and claude.ai to the referral sources for order attribution tracking. We're adding 'AI' as a new channel. The PR makes it easier to test these attribution changes in WooCommerce Analytics.

How to test the changes in this Pull Request:

1. Using this branch, generate a large number of test orders
2. Go to /wp-admin/admin.php?page=wc-orders
3. Confirm that there are orders with Origin set to Referral: Chatgpt.com or Referral: Claude.ai

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Other information:

• Have you added an explanation of what your changes do and why you'd like us to include them?
• Have you written new tests for your changes, as applicable?
• Have you successfully run tests with your changes locally?

Changelog entry

Add AI sources to order attribution data

FOR PR REVIEWER ONLY:

• I have reviewed that everything is sanitized/escaped appropriately for any SQL or XSS injection possibilities. I made sure Linting is not ignored or disabled.

[louwie17]

Thanks for adding this, this tested well :)