Add shard train-00005-of-00018.parquet (7/20)

Add shard train-00004-of-00018.parquet (6/20)

Add shard train-00003-of-00018.parquet (5/20)

Add shard train-00002-of-00018.parquet (4/20)

Add shard train-00001-of-00018.parquet (3/20)

Add shard train-00000-of-00018.parquet (2/20)

Add shard test-00000-of-00001.parquet (1/20)

5GB: update README for sharded parquet 50M

Viewer fix: keep only default parquet config (json still in repo as files, not viewer config) + Problem Types above Quickstart

Fix viewer: json array -> jsonl lines + move Problem Types above Quickstart

Docs: clarify parquet/json dual folders and working load_dataset examples

Remove legacy data/ folder - migrated to parquet/ + json/

Reorganize into parquet/ and json/ folders + remove em dashes - verified dual configs

Remove license comparison section

Initial release: 150K verified arithmetic reasoning (v4) with tiered difficulty

initial commit