ci: use pnpm/setup and devEngines

[danielroe]

🔗 Linked issue

❓ 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

this uses the new https://github.com/pnpm/setup github action to replace actions/setup-node + corepack, as corepack is going away in node 26+ 😢

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[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 28.35%. Comparing base (6d77b77) to head (4899223).
⚠️ Report is 1 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #1026   +/-   ##
=======================================
  Coverage   28.35%   28.35%           
=======================================
  Files          12       12           
  Lines         328      328           
  Branches       98       98           
=======================================
  Hits           93       93           
  Misses        235      235           

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