🔗 Linked issue

resolves nuxt/nuxt#13383

❓ Type of change

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

📚 Description

This PR exposes nuxt3/app (for #app), nuxt3/pages and nuxt3/meta (for #meta) as the runtime entrypoints for those respective parts of nuxt3.

This means that module or library authors, for example, can benefit from nuxt3 types without needing to use a generated .nuxt/tsconfig.json.

Because TypeScript isn't quite ready for types for export paths (track in microsoft/TypeScript#33079), we add declaration files at the project root for IDE auto-complete. Both webpack & vite properly respect subpath exports, however, and resolve any imports we need.

Because this is additive, users can continue importing from '#app' - and indeed I would recommend pending any updates to the user-facing docs until nuxt3/bridge are in sync (e.g. both importing from nuxt/app or equivalent), perhaps when we move to RC.

⚠️ Note: Adopting package subpath exports is inherently risky because it breaks any other possible imports/access to the package, so we should take special care to ensure that ... ⚠️

📝 Checklist

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