Feature request: device size presets / responsive preview in the Preview window

Summary

The Preview window currently shows the app at a fixed size. It would be very useful to be able to quickly switch between common device size presets (mobile, tablet, desktop) or set a custom viewport, similar to browser DevTools' responsive mode.

Requested features

• Device preset buttons (e.g. Mobile 375px, Tablet 768px, Desktop 1280px, Full width)
• Custom width/height input
• Orientation toggle (portrait / landscape)
• Optional: display current dimensions

Expected behavior

The Preview window has a toolbar or resize controls that let the user switch viewport sizes without manually resizing the window. Claude can also use these when verifying responsive layouts.

Current behavior

The preview renders at whatever size the preview panel happens to be. There is no way to quickly test a specific viewport size.

Use case

Responsive design work — verifying that layouts look correct at mobile, tablet, and desktop breakpoints without leaving the IDE.