[Bugfix]: Fix Step3ReasoningParser missing is_reasoning_end_streaming (#31969)

Signed-off-by: chaunceyjiang <chaunceyjiang@gmail.com>

vllm/reasoning/step3_reasoning_parser.py

@@ -100,6 +100,12 @@ class Step3ReasoningParser(ReasoningParser):
     def is_reasoning_end(self, input_ids: list[int]) -> bool:
         return self.think_end_token_id in input_ids
 
+    def is_reasoning_end_streaming(
+        self, input_ids: list[int], delta_ids: list[int]
+    ) -> bool:
+        end_token_id = self.think_end_token_id
+        return end_token_id in delta_ids
+
     def extract_content_ids(self, input_ids: list[int]) -> list[int]:
         if self.think_end_token_id not in input_ids[:-1]:
             return []