perf(nuxt): mark payload as shallowReactive

[danielroe]

🔗 Linked issue

resolves #26825

❓ 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 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

This improves performance by not marking the entire Nuxt payload as reactive - but granularly enabling shallow reactivity first in the parts of it that we need to be reactive.

📝 Checklist

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

[stackblitz]

Run & review this pull request in StackBlitz Codeflow.

[daniluk4000]

That's sick 🔥

[Mini-ghost]

@danielroe

Since this PR marks payload as shallowReactive, should the reactive that was removed in this PR #26558 be restored? Or, as mentioned at the PR end, does runtimeConfig not require reactivity?

[danielroe]

I think it might not require reactivity at all.