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

Dataset card refresh + promote CHANGELOG.md as primary release history (#19)

README: replace dataset_info with per-task configs so HF viewer loads each schema independently (#20)

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

Add markdown LICENSE and point license_link to LICENSE.md

Update dataset card with task overview figure and HF link

Update review comments

Update README.md

initial commit