Portable Stories: Fix injected root element changing layout

[JReinhold]

Closes #26368

What I did

In composeStory, instead of injecting a root element to serve as the default canvasElement for play-functions, we're now just relying on document.body instead, which should work in 99 % of use cases involving Vitest, Jest, Playwright, etc. For the edge cases where document.body isn't correct - eg. you're rendering the composed story deep in on a site, you're still able to overwrite the canvasElement by just passing an element to play().

cc @dannyhw this might not work for React Native, but AFAIK play-functions don't work at all in React Native, so this is probably an issue for the future? "Worst case" users can always pass a canvasElement.

Checklist for Contributors

Testing

The changes in this PR are covered in the following automated tests:

• stories
• unit tests
• integration tests
• end-to-end tests

Manual testing

This section is mandatory for all contributions. If you believe no manual test is necessary, please state so explicitly. Thanks!

Documentation

• Add or update documentation reflecting your changes
• If you are deprecating/removing a feature, make sure to update
  MIGRATION.MD

Checklist for Maintainers

• When this PR is ready for testing, make sure to add ci:normal, ci:merged or ci:daily GH label to it to run a specific set of sandboxes. The particular set of sandboxes can be found in code/lib/cli/src/sandbox-templates.ts

• Make sure this PR contains one of the labels below:

  Available labels

  • bug: Internal changes that fixes incorrect behavior.
  • maintenance: User-facing maintenance tasks.
  • dependencies: Upgrading (sometimes downgrading) dependencies.
  • build: Internal-facing build tooling & test updates. Will not show up in release changelog.
  • cleanup: Minor cleanup style change. Will not show up in release changelog.
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  • other: Changes that don't fit in the above categories.

🦋 Canary release

This pull request has been released as version 0.0.0-pr-26387-sha-0dbe3e46. Try it out in a new sandbox by running npx storybook@0.0.0-pr-26387-sha-0dbe3e46 sandbox or in an existing project with npx storybook@0.0.0-pr-26387-sha-0dbe3e46 upgrade.

More information

Published version	0.0.0-pr-26387-sha-0dbe3e46
Triggered by	@JReinhold
Repository	storybookjs/storybook
Branch	jeppe/composed-play-default-canvaselement
Commit	0dbe3e46
Datetime	Fri Mar 8 13:40:48 UTC 2024 (1709905248)
Workflow run	8204148038

To request a new release of this pull request, mention the @storybookjs/core team.

core team members can create a new canary release here or locally with gh workflow run --repo storybookjs/storybook canary-release-pr.yml --field pr=26387

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[dannyhw]

Happy to test on RN if you have a canary or after release. Seems ok though.

[yannbf]

Great stuff! Thanks <3