* unicode : add opt-in NFC normalization for Unigram tokenizers
Note: used help from Codex, Sol 6.1 Medium
* Fixing initial bot comments + linter error (using existing out instead of print)
* removed test_nfc_tokenizer
The collapsed \p{S} class was missing '~', which split " ~" into
separate pre-tokens and prevented the Ġ~ BPE merge used by DeepSeek V4.
This caused re-tokenized prompts to diverge from sampled tokens and
broke KV cache reuse.
Assisted-by: Codex
Sandro Hanea
Thiago Padilha