CI: use non-recursive submodule init (ard has broken nested submodules)

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: 2 people

.github/workflows/tests.yml

@@ -9,8 +9,8 @@ jobs:
 
     steps:
       - uses: actions/checkout@v3
-        with:
-          submodules: true
+      - name: Init submodules (non-recursive)
+        run: git submodule update --init
       - name: Set up Python 3.11
         uses: actions/setup-python@v3
         with: