docs(AI): move MCP clients into Tabs

[reidbarber]

Updates the S2 and React Aria /ai pages to where the individual MCP client guides are inside Tabs.

This is similar to the Framework Setup section in our getting started page.

By removing all those subsections, it is easier to discover the remaining sections on the page (Agent Skills, etc.).

✅ Pull Request Checklist:

• Included link to corresponding React Spectrum GitHub Issue.
• Added/updated unit tests and storybook for this change (for new code or code which already has tests).
• Filled out test instructions.
• Updated documentation (if it already exists for this component).
• Looked at the Accessibility Practices for this feature - Aria Practices

📝 Test Instructions:

Check the updated pages:

• Working with AI | React Spectrum
• Working with AI | React Aria

🧢 Your Project: