Preview: Add visual indicator when Claude is controlling the browser preview

Problem

When Claude is actively controlling the browser preview (via , , , etc.), there is no visual indicator on the preview window that automation is in progress.

This makes it easy for the user to accidentally click or type in the preview while Claude is mid-action — causing race conditions, unexpected state, or just confusion about who is driving.

Suggested Solution

Add a visible border or overlay to the preview window while Claude is actively interacting with it. Some ideas:

• Orange/amber gradient border around the preview viewport (similar to how the Claude in Chrome extension shows an orange pulsing border when Claude is controlling the browser)
• An orange cursor or cursor overlay so it's clear that Claude is "driving"
• A small floating badge (e.g. "Claude is driving...") in the corner of the preview

The indicator should:

• Appear when a tool call is in flight
• Disappear when Claude's turn ends or when no tool calls are active
• Be unobtrusive but clearly visible

Why This Matters

• Users instinctively interact with the preview (it looks like a normal browser)
• Clicking while Claude is mid-action can break the automation flow
• The Chrome extension already solves this with an orange border — preview should match that UX

Environment

• Claude Code desktop app on Windows
• Using tools for frontend verification