ci: Add ty typecheck to pythonpackage.yml lint job

- Ensure both ruff and ty run in main CI workflow
- Matches lint.yml workflow which has both checks
- All code quality checks now run automatically

Author: vinitkumar

.github/workflows/pythonpackage.yml

@@ -121,3 +121,6 @@ jobs:
     - name: Run ruff
       run: uvx ruff check json2xml tests
 
+    - name: Run ty typecheck
+      run: uvx ty check json2xml tests
+