Remove Python 3.9 from pytest CI matrix

Co-Authored-By: Claude <noreply@anthropic.com>

Author: claude

.github/workflows/tests.yml

@@ -16,7 +16,7 @@ jobs:
       fail-fast: false
       matrix:
         os: [ubuntu-latest, windows-latest, macos-latest]
-        python-version: ["3.9", "3.10", "3.11", "3.12"]
+        python-version: ["3.10", "3.11", "3.12"]
 
     steps:
     - uses: actions/checkout@v7