[Bugfix] Fix Harmony preamble visibility in Responses API (#32114)

Signed-off-by: Pushkar Patel <git@thepushkarp.com>
Signed-off-by: pupa <pupa@users.noreply.github.com>

vllm/entrypoints/openai/chat_completion/stream_harmony.py

@@ -147,7 +147,7 @@ def extract_harmony_streaming_delta(
                         function=DeltaFunctionCall(arguments=group.text),
                     )
                 )
-        elif group.channel == "commentary":
+        elif group.channel == "commentary" and group.recipient is None:
             # Tool call preambles meant to be shown to the user
             combined_content += group.text
             content_encountered = True