fix(ci): pin single Python version to match pre-uv test behavior

Set UV_PYTHON to skip the multi-Python loop while still running both
pydantic v2 and v1 tests. This matches the old rye-based CI behavior
(2 test runs instead of 3).

Author: musa-cf

.github/workflows/ci.yml

@@ -97,12 +97,9 @@ jobs:
         run: ./scripts/bootstrap
 
       - name: Run tests
-        run: |
-          echo "==> Running tests with Pydantic v2 (Python >=3.9.0)"
-          uv run --isolated --all-extras pytest
+        run: ./scripts/test
         env:
           UV_PYTHON: ">=3.9.0"
-          DEFER_PYDANTIC_BUILD: "false"
 
   examples:
     timeout-minutes: 10