viewer: add configs YAML + metadata.jsonl for 2dbbox & dense_captioning

Dataset card refresh + promote CHANGELOG.md as primary release history (#20)

README: replace dataset_info with per-task configs so HF viewer loads each schema independently (#21)

Declare test-only split in dataset_info frontmatter

Point License section to LICENSE.md in dataset

Remove paper citation TBD reminder

Move task overview figure from Dataset Description to References

Mirror VANTAGE-Bench dataset card and add markdown LICENSE

initial commit