Fix coverage file name

Author: hosaka

.github/workflows/main.yml

@@ -61,7 +61,7 @@ jobs:
         run: |
           uv run coverage combine --quiet
           uv run coverage report --sort=cover
-          mv .coverage .coverage-${{ matrix.os }}
+          mv .coverage .coverage.${{ matrix.os }}
 
       - name: Upload coverage artifacts
         uses: actions/upload-artifact@v4