[Bug]: UserGlobal changes when editing global on a story level

[valentinpalkovic]

Describe the bug

As soon as a global value like globals: {backgrounds: {value: 'dark'}} is set on a story level, after the HMR event, the userGlobal value is set, leading to a change in the URL and in the background toolbar

Reproduction link

storybookjs/storybook-rsc-demo#20

Reproduction steps

1. Open Storybook
2. Go to a story
3. Define the background for a story
4. See the url changing and the userGlobal is set. Switching to another story will persist the global value.

Additional context

No response

[yannbf]

Additionally, I managed to reproduce this (maybe it's a different issue?) on Mealdrop:

1. Go to Button stories file, write this:

export const Disabled: Story = {
  globals: {
    backgrounds: {
      value: 'dark'
    }
  },
}

2. See that story in Storybook
3. Go to preview, write this:

const preview: Preview = {
  initialGlobals: {
    viewport: { value: 'responsive' },
    backgrounds: {
      value: 'light', // add backgrounds
    },
  },
  //...
}

4. See the URL getting changed to http://localhost:6006/?path=/story/components-button--default&globals=backgrounds.value:dark when it shouldn't