Add special_tokens_map.json required by fastembed-rs tokenizer loader

Add tokenizer_config.json required by fastembed-rs tokenizer loader

Add config.json required by fastembed-rs tokenizer loader

Add tokenizer.json (from minishlab/potion-code-16M-v2)

Add ONNX export (opset 17, float32, mean-pool + L2-norm baked in)

initial commit