Enable walltime for codspeed

https://codspeed.io/docs/instruments/walltime

Author: saulshanabrook

.github/workflows/CI.yml

@@ -49,7 +49,7 @@ jobs:
       - run: make stubtest
 
   benchmark:
-    runs-on: ubuntu-latest
+    runs-on: codspeed-macro
     steps:
       - uses: actions/checkout@v4
       - uses: astral-sh/setup-uv@v6