[Bug]: Viewports aren’t reset when navigating away from a story with a default viewport

[JReinhold]

Describe the bug

When navigating to a story with a defaultViewport, that viewport is correctly applied, and the globals query param in the URL is updated accordingly. When navigating away to a story without an explicit viewport, the global stays there, meaning that the viewport is still applied, even though the story doesn't have a default viewport.

To Reproduce

• Open a regular story without a viewport: https://next--635781f3500dd2c49e189caf.chromatic.com/?path=/story/components-modal--fixed-height
• Navigate to the story Manager/Mobile/About/Default - which has a default mobile viewport
• Navigate to a story without a viewport like Components/Modal/Default
• See that the mobile viewport is still applied even though it’s not part of that story

System

Storybook 8.1.0-alpha.8

Additional context

No response

[shilman]

I updated the viewports addon to store its state in globals in 8.0 as a step towards standardizing on globals for most addon state. This results in the behavior you describe and I don't plan to fix this.

@tmeasday is working on global overrides per #23347 and if those are finished it would have the desired behavior you describe when completed.