refactor: consolidate python/tests/ into tests/ directory

Move all Python test files from python/tests/ to the top-level tests/
directory to match the project's CONTRIBUTING.md guidelines. Update
sys.path inserts and template path references to reflect the new
location.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

pytest.ini

@@ -7,7 +7,7 @@ python_classes = Test*
 python_functions = test_*
 
 # Test paths
-testpaths = tests python/tests
+testpaths = tests
 
 # Minimum Python version
 minversion = 6.0