fix: preventFocus TypeError on window focus/blur during a press

[microbit-matt-hillsdon]

preventFocus attaches focus and blur listeners to the window. When the window itself gains or loses focus the target is Window not a Node. Both helpers passed it straight into nodeContains, so Node.contains threw:

TypeError: Failed to execute 'contains' on 'Node': parameter 1 is not of type 'Node'.

Guard both calls with isNode and add a usePress test.

Fixes #10591

Closes

✅ 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:

I clicked around some storybook cases that exercise preventFocus (e.g. number field +/-) but that's for the happy path not so much the bug which was hard to reproduce, likely due to RAF timing, but seen in error logs.

🧢 Your Project:

micro:bit Python Editor