fix(module): put back #build/ui.css alias

[benjamincanac]

🔗 Linked issue

Resolves #5487, resolves #5501

❓ Type of change

• 📖 Documentation (updates to the documentation or readme)
• 🐞 Bug fix (a non-breaking change that fixes an issue)
• 👌 Enhancement (improving an existing functionality)
• ✨ New feature (a non-breaking change that adds functionality)
• 🧹 Chore (updates to the build process or auxiliary tools and libraries)
• ⚠️ Breaking change (fix or feature that would cause existing functionality to change)

📚 Description

When Prettier or Tailwind CSS IntelliSense reads a CSS file that imports @nuxt/ui, they fail to resolve the #build/ui.css import from src/runtime/index.css.

This virtual file is dynamically generated for Nuxt and Vite based on theme configuration, but Prettier and IntelliSense don't have access to Vite's alias resolution.

This PR adds a static alias using Node.js subpath imports so tooling can resolve it via standard module resolution.

Runtime (Nuxt/Vite) continues using dynamic resolution, while tooling uses the static fallback. The static file is built at package publish time with default theme configuration, so custom themes won't be reflected in IntelliSense. It's not perfect but better than nothing for now.

📝 Checklist

• I have linked an issue or discussion.
• I have updated the documentation accordingly.

[pkg-pr-new]

npm i https://pkg.pr.new/@nuxt/ui@5499

commit: 6ceed3b