fix(nemotron): deepseek-r1 num_predict 400→1200，避免 <think> block 截斷後空回覆

deepseek-r1:14b 思考 token 超過 400 會在 </think> 前截斷，導致
清理後 body 為空，Telegram 顯示空訊息。
- chat_manager: num_predict 400 → 1200
- telegram_gateway: _clean_ai_reply 空值加 fallback 錯誤提示

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

apps/api/src/services/chat_manager.py

@@ -180,7 +180,7 @@ class ChatManager:
                             {"role": "system", "content": system_prompt},
                             {"role": "user", "content": user_message},
                         ],
-                        "options": {"num_predict": 400},
+                        "options": {"num_predict": 1200},
                     },
                 )
                 resp.raise_for_status()

apps/api/src/services/telegram_gateway.py

@@ -3718,7 +3718,7 @@ class TelegramGateway:
                 f"{context}\n用戶 {username} 在 SRE 戰情室問你：",
                 clean_text,
             )
-            body = _clean_ai_reply(result) if result else '🔴 無響應 (NIM 超時)'
+            body = (_clean_ai_reply(result) if result else '') or '🔴 無響應 (deepseek-r1 超時或思考截斷)'
             await self.send_as_nemotron(
                 text=f"🤖 <b>NemoClaw</b>\n\n{body}",
                 reply_to_message_id=message_id,
@@ -3741,8 +3741,9 @@ class TelegramGateway:
                 )
 
             if nemo_result and not isinstance(nemo_result, Exception):
+                nemo_body = _clean_ai_reply(nemo_result) or "🔴 回覆清理後為空 (deepseek-r1 思考超時)"
                 await self.send_as_nemotron(
-                    text=f"🤖 <b>NemoClaw</b>\n\n{_clean_ai_reply(nemo_result)}",
+                    text=f"🤖 <b>NemoClaw</b>\n\n{nemo_body}",
                     reply_to_message_id=message_id,
                 )