Documents the content-author contract for catalog item GLBs: slot_
material naming + deriveSlotId rules, authored defaults and
pascal_material extras, the cutout reserved mesh, the ~1 UV unit/m world
scale, vertex colours for fixed detail, and the validated Blender + glTF
export recipe (Custom Properties export gotcha, gltfpack -ke extras
preservation). Indexes the page in the architecture README and links it
from materials-and-themes.md (previously a dangling "phase-6 Blender
recipe" reference).
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
