Update grok.py and tiktoken tokenizer (#9532)

python/sglang/srt/hf_transformers_utils.py

@@ -263,6 +263,11 @@ def get_tokenizer(
     **kwargs,
 ) -> Union[PreTrainedTokenizer, PreTrainedTokenizerFast]:
     """Gets a tokenizer for the given model name via Huggingface."""
+    if tokenizer_name.endswith(".json"):
+        from sglang.srt.tokenizer.tiktoken_tokenizer import TiktokenTokenizer
+
+        return TiktokenTokenizer(tokenizer_name)
+
     if tokenizer_mode == "slow":
         if kwargs.get("use_fast", False):
             raise ValueError("Cannot use the fast tokenizer in slow tokenizer mode.")