Adds integration tests exercising the full ReorientFaceMesh ->
RenderTexturedFaceMesh data flow with synthetic inputs, verifying output
shape contracts and value ranges. Also adds pytest.ini and conftest.py
for standalone test execution, guards __init__.py relative imports with
try/except for pytest 8.x Package compatibility, and removes tests/ from
.gitignore.
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
