fix(nuxt): ensure typed layout prop persists through build

[94726]

🔗 Linked issue

#22847

❓ Type of change

• 📖 Documentation (updates to the documentation, readme or JSdoc annotations)
• 🐞 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)
• 🧹 Chore (updates to the build process or auxiliary tools and libraries)
• ⚠️ Breaking change (fix or feature that would cause existing functionality to change)

📚 Description

The issue started because of 0d9a0b7. For some reason the ? makes it so that the type is changed. I have no idea why but this seems to fix it. Would appreciate an explaination if someone knows why :)
To me, it looks like a bug of unbuild/dts generation.
Maybe not a bug per se, but it looks like it tries to evaluate the type at build time and in this case probably doesn't find PageMeta?

📝 Checklist

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

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[danielroe]

This looks good. You're right that it's an upstream issue in mkdist that we likely need to resolve there as well. Likely will be solved in unjs/mkdist#154.