Running the tests

Both suites ship with the add-on repository.

```
blender --background --factory-startup --python tests/test_register.py
blender --background --factory-startup --python tests/test_render.py
```

The first is GPU-free — registration, colour maths, palette integrity and stability, node injection, compositor cleanliness, teardown, handler persistence. The second drives a real render and asserts the exported image contains exactly one colour per material plus background, each covering an identical pixel count.

The first runs in CI on Blender 4.2 and 5.2. The second needs a GL context that CI runners do not have, so it is a local check.