chore: update docs around host attr reflection for SSR

[Jane Chu (janechu)]

Pull Request

📖 Description

This clarifies the host attribute reflection doc on caveats for SSR.

✅ Checklist

General

• I have included a change request file using $ npm run change
• I have added tests for my changes.
• I have tested my changes.
• I have updated the project documentation to reflect my changes.
• I have read the CONTRIBUTING documentation and followed the standards for this project.

Agents

• I have linked to an existing issue in this project that this change addresses
• I have read the skills
• I have read the DESIGN.md file(s) in packages relevent to my changes
• I have updated the DESIGN.md file(s) in packages relevent to my changes