Add official-URDF fetch notes and stdlib morph apply script

Enable Dataset Viewer catalogs; rewrite dataset card

Disable dataset viewer splits; show Download on the card

Add jsonl catalogs for Hugging Face datasets.load_dataset

Dataset card: Hub tags, load_dataset configs, retrieval keywords

English dataset card and docs; keep appearance maps and morph specs

Initial appearance swatches, albedo maps, and morph/composition specs

initial commit