Revert to PyPy 3.10 to avoid known numeric handling issues

Author: claude

.github/workflows/ci.yml

@@ -26,7 +26,7 @@ jobs:
     runs-on: ubuntu-latest
     strategy:
       matrix:
-        python-version: ["3.10", "3.11", "3.12", "3.13", "3.14", "pypy-3.11"]
+        python-version: ["3.10", "3.11", "3.12", "3.13", "3.14", "pypy-3.10"]
       fail-fast: false
     steps:
     - uses: actions/checkout@v6