Organize tools and move Python tests into tools/tests

docs/blender-assets.md

@@ -187,7 +187,7 @@ carry baked AO and the shared neutral material maps described above.
   during LOD generation), budgets (library characters 8000/8000, base fallback 6000/4000, gear 1500, props 4000
   triangles), grounding, and an editable `.blend`. For characters it also
   checks skinning, bones, slots, the `npc_base` mesh node and the height.
-- `tools/test_blender_assets.py`: catalogue and contract consistency with
+- `tools/tests/test_blender_assets.py`: catalogue and contract consistency with
   `npc_pipeline.py`, plus a clean audit and full manifest coverage when the
   library is built.
 - `src/test/tests/test_blender_assets.gd`: every asset imports as a scene