Normalize example naming order

Remove obsolete file: examples/downstream/__pycache__/03_batch_integration_eval.cpython-39.pyc

Remove obsolete file: examples/downstream/__pycache__/02_zero_shot_logreg.cpython-39.pyc

Remove obsolete file: examples/downstream/__pycache__/01_finetune_classification.cpython-39.pyc

Remove obsolete file: examples/__pycache__/0_preprocess_to_input_ids.cpython-39.pyc

Remove obsolete file: examples/downstream/99_pretrain_from_scratch_reference.py

Remove obsolete file: examples/downstream/98_continue_pretraining_reference.py

Remove obsolete file: examples/downstream/03_batch_integration_eval.py

Remove obsolete file: examples/downstream/02_zero_shot_logreg.py

Remove obsolete file: examples/downstream/01_finetune_classification.py

Remove obsolete file: examples/1_extract_embeddings.py

Remove obsolete file: examples/0_preprocess_to_input_ids.py

Add full downstream examples and legacy scripts

Add preprocess docs, examples, tokenizer mapping assets