docs: add arXiv:2605.18232 citation, badge, and paper reference

Remove redundant validation.jsonl (replaced by validation.parquet)

Update dataset card YAML for parquet shards

Add train-00001-of-00004.parquet (parquet/zstd)

Add train-00002-of-00004.parquet (parquet/zstd)

Add train-00003-of-00004.parquet (parquet/zstd)

Add train-00000-of-00004.parquet (parquet/zstd)

Add validation.parquet (parquet/zstd)

Add validation split (40,967 docs / ~15M tokens)

Add SHASUMS manifest

Add manual inspection sample (20 docs)

Add HPLT-raw comparison tokenizer

Add SomaliWeb v1 BPE-16K tokenizer

Add dataset card

initial commit