Make floating preview controls easier to discover on mobile

[rywible]

Problem

On Android Chrome, I initially thought there was no way to dismiss the floating screen that shows the agent using the browser. I had no idea the small corner dot was tappable or that it revealed the toolbar and close button.

The documented phone workflow already supports this. This is a discoverability and accessibility concern: the low-contrast dot does not look like a control, and touch users have no hover cue to reveal what it does.

Two possible directions

1. Make the dot more noticeable. Increase its contrast, perhaps with a brief pulse to draw attention to the tap target. Any pulse should respect reduced-motion preferences, avoid continuous animation, and stay distinguishable from the existing recording indicator.
2. Use a recognizable control icon. Replace the dot with a settings or drawer/menu icon that suggests it opens controls. That would communicate the existing action without relying on animation.

The goal is for a mobile user to discover how to reveal the existing controls, including closing the floating preview, without needing to read the documentation first.

Scope and request for direction

I am proposing a small change to the affordance for the existing floating-preview toolbar, keeping its current actions and dismissal behavior. I searched related discussions; #6956 concerns the device toolbar inside preview chrome, and #16584 concerns opening the preview page in a system browser, rather than discovering this corner control.

Following the contribution guide, I would like maintainer approval of the direction and scope before implementing or opening a PR. Would improving this mobile affordance be welcome? Which of the two directions fits the intended design better, and are there constraints you would want a contribution to follow?

Prepared with Codex (gpt-6.1-sol) through T3 Code.