Docs: Update install prompt to use npm create

[kylegach]

This PR contains the exact changes in #34828, but targets main (because we need the changes to be in the latest docs quickly).

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.

Summary by CodeRabbit

• Documentation
  • Updated Storybook installation instructions across the documentation.

[github-actions]

	Fails
🚫	This PR targets main, but it should target next. Please update the base branch of your PR.
🚫	PR description is missing the mandatory "#### Manual testing" section. Please add it so that reviewers know how to manually test your changes.

Generated by 🚫 dangerJS against 5f2e724

[coderabbitai]

No actionable comments were generated in the recent review. 🎉

ℹ️ Recent review info

⚙️ Run configuration

Configuration used: Organization UI

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Run ID: f4d2f537-4f87-44d3-a8b5-1f5c74a1be08

📥 Commits

Reviewing files that changed from the base of the PR and between f8c16d1 and 5f2e724.

📒 Files selected for processing (3)

• docs/_snippets/prompt-install-storybook.md
• docs/get-started/install.mdx
• docs/index.mdx

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📝 Walkthrough

Walkthrough

The PR updates documentation across three files to replace the Storybook installation command from npx storybook@latest init with npm create storybook@latest, ensuring consistent setup instructions in the reusable snippet, getting started guide, and homepage.

Changes

Storybook Installation Command

Layer / File(s)	Summary
Installation command updates docs/_snippets/prompt-install-storybook.md, docs/get-started/install.mdx, docs/index.mdx	Storybook initialization instructions are updated from npx storybook@latest init to npm create storybook@latest across the reusable prompt snippet, getting started guide, and homepage callouts.

Estimated code review effort

🎯 1 (Trivial) | ⏱️ ~2 minutes

Possibly related PRs

• storybookjs/storybook#34648: Changes the same Storybook command in the prompt-install-storybook snippet and related documentation files.

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