fix(ci): run tests with single Python version and pydantic v2 only

The full matrix (2 Python versions x 2 pydantic versions = 3 runs)
causes CI timeouts. Run only min Python + pydantic v2 to keep CI
within the 30 minute budget. The full matrix can be run manually
via scripts/test when needed.

Author: musa-cf

.github/workflows/ci.yml

@@ -97,7 +97,12 @@ jobs:
         run: ./scripts/bootstrap
 
       - name: Run tests
-        run: ./scripts/test
+        run: |
+          echo "==> Running tests with Pydantic v2 (Python >=3.9.0)"
+          uv run --isolated --all-extras pytest
+        env:
+          UV_PYTHON: ">=3.9.0"
+          DEFER_PYDANTIC_BUILD: "false"
 
   examples:
     timeout-minutes: 10