Separate TTS text from metadata tokens in respond()

Filter __meta dict tokens from TTS accumulator so progress messages
([LangGraph], thinking blocks, source references) are displayed in chat
but not read aloud. Answer tokens continue to accumulate in tts_text.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

app.py

@@ -105,12 +105,18 @@ async def respond(message, history, show_thinking, user_id, use_tts, run_ids):
     yield history, "", None, run_ids
 
     collected_run_id: str | None = None
+    tts_text = ""  # 순수 답변만 누적 (메타 토큰 제외)
     try:
         async for token, run_id in api_client.chat(message, user_id, show_thinking):
             if run_id is not None:
                 collected_run_id = run_id
                 break
-            history[-1]["content"] += token
+            if isinstance(token, dict) and "__meta" in token:
+                display_token = token["__meta"]
+            else:
+                display_token = token
+                tts_text += display_token
+            history[-1]["content"] += display_token
             yield history, "", None, run_ids
     except Exception as e:
         history[-1]["content"] += f"\n\n[오류: {e}]"
@@ -120,7 +126,7 @@ async def respond(message, history, show_thinking, user_id, use_tts, run_ids):
     run_ids.append(collected_run_id)
 
     if use_tts:
-        audio_path = await tts_speak(history[-1]["content"])
+        audio_path = await tts_speak(tts_text)
         yield history, "", audio_path, run_ids
     else:
         yield history, "", None, run_ids