feat(edit): replace small-model selector with keyword + parametric assembler

docs(plan): 100-part catalog + live-3D reports plan

docs(plan): template part-assembly edit path implementation plan

docs(plan): voxel render polish + freeform style implementation plan

feat(tools): add voxel-model-eval harness + skill

feat: freeform voxel generation (Gemma 4 12B) + freeform breeding

docs: spec + plan for the two-page splice flow