Update ML Intern artifact metadata

Add selective HF parquet shard download support (--hf-files, --hf-subdir, --max-shards, --list-shards)

Fix config validation: text_column lives under source.text_column

Update ML Intern artifact metadata

Add YAML metadata to README

Update ML Intern artifact metadata

Initial GrandLine implementation: deterministic shard-first dataset preprocessing for LLM pretraining

Update ML Intern artifact metadata

initial commit