fix: use decoded asset id to access prerendered asset header overrides

[danielroe]

🔗 Linked issue

❓ 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

Add test - sorry!

📝 Checklist

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

[codecov]

Codecov Report

Merging #1588 (3379c2c) into main (39851b8) will not change coverage.
The diff coverage is 100.00%.

@@           Coverage Diff           @@
##             main    #1588   +/-   ##
=======================================
  Coverage   76.26%   76.26%           
=======================================
  Files          76       76           
  Lines        7799     7799           
  Branches      781      781           
=======================================
  Hits         5948     5948           
  Misses       1849     1849           
  Partials        2        2           

Files Changed	Coverage Δ
src/rollup/plugins/public-assets.ts	92.68% <100.00%> (ø)