Add paginated thumbnail catalog for 1,400 SimReady assets
Add a spreadsheet-style asset browser to the dataset page with thumbnail, package name, and main USD link columns. The catalog covers all 1,400 packages and uses 256-pixel copies of their existing previews.
The README explicitly selects catalog/assets.parquet for the native dataset viewer, providing pagination and search. Existing asset paths and contents are unchanged, and no repository access settings are modified.
Includes a refresh script and maintenance instructions. Automatic scheduling is not enabled; the script can be called after asset publication and creates a refresh PR.
Validation: all 1,400 packages have one main USD and an exact matching thumbnail; every embedded image decodes at 256 x 256; Hugging Face Datasets loads 1,400 rows with an Image feature; dataset-card metadata validates. Catalog size: 76 MB. Live viewer processing must be checked after merge.