Preview tool: allow user to resize viewport from UI

Feature Request

The preview_resize tool allows Claude to programmatically resize the preview viewport, but there is no way for the user to resize or switch presets directly from the preview UI.

Use Case

When doing responsive UI work, I frequently need to check layouts at different breakpoints (mobile 375px, tablet 768px, desktop 1280px, wide 1536px+). Currently I have to ask Claude to run preview_resize each time, which adds a round-trip.

Proposal

Add a viewport size selector to the preview panel UI:

• A dropdown or segmented control with common presets (Mobile / Tablet / Desktop / Native)
• Or a draggable resize handle on the preview frame edges
• Bonus: show current viewport dimensions somewhere in the preview chrome

This would make responsive development workflows much faster since the user can toggle sizes without going through the chat.

Current Workaround

Ask Claude to call preview_resize with the desired preset or dimensions each time.