Core: Improve file path resolution on Windows

[yannbf]

Closes #32872

What I did

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-storybook/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.
  • documentation: Documentation only changes. Will not show up in release changelog.
  • feature request: Introducing a new feature.
  • BREAKING CHANGE: Changes that break compatibility in some way with current major version.
  • other: Changes that don't fit in the above categories.

🦋 Canary release

This pull request has been released as version 0.0.0-pr-32893-sha-331baf0a. Try it out in a new sandbox by running npx storybook@0.0.0-pr-32893-sha-331baf0a sandbox or in an existing project with npx storybook@0.0.0-pr-32893-sha-331baf0a upgrade.

More information

Published version	0.0.0-pr-32893-sha-331baf0a
Triggered by	@yannbf
Repository	storybookjs/storybook
Branch	yann/fix-preset-path-joining-windows
Commit	331baf0a
Datetime	Thu Oct 30 11:39:01 UTC 2025 (1761824341)
Workflow run	18939383750

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 publish.yml --field pr=32893

Summary by CodeRabbit

• Chores
  • Switched internal path utility implementation to an alternative path library across the codebase; no runtime behavior or public APIs changed.
• Tests
  • Updated tests to use normalized path comparisons and adjusted expectations to align with the new path utilities.

[nx-cloud]

View your CI Pipeline Execution ↗ for commit 1b61b21

Command	Status	Duration	Result
nx run-many -t build --parallel=3	✅ Succeeded	45s	View ↗

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☁️ Nx Cloud last updated this comment at 2025-10-30 13:25:04 UTC

[storybook-app-bot]

Package Benchmarks

^{Commit: 1b61b21, ran on 30 October 2025 at 13:15:03 UTC}

The following packages have significant changes to their size or dependencies:

@storybook/nextjs-vite

	Before	After	Difference
Dependency count	124	124	0
Self size	3.83 MB	3.83 MB	0 B
Dependency size	21.54 MB	21.57 MB	🚨 +28 KB 🚨
Bundle Size Analyzer	Link	Link