fix: ios26 address bar

[nwidynski]

Fixes overlays being positioned underneath the address bar in iOS 26.

Pulled out of #10102 to make the original PR smaller and easier to review.

✅ 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
• I understand every change in this PR and can explain why it's there.
• If AI-assisted, I followed our AI contribution guidance and pointed my assistant at CLAUDE.md.

📝 Test Instructions:

🧢 Your Project:

[snowystinger]

To test this, go to react-aria/Modal and open the first example. The top of the modal won't be off the screen to the top.