fix(botops): fix reasoning panel appearing after AI response and filter conversation start notification

- Add _ai_prefab flag to track pre-created empty AI widget
- start_reasoning() now reorders widgets: remove empty AI widget, mount reasoning first, then remount AI widget
- This ensures reasoning always appears BEFORE the actual answer
- Filter out 'Conversation started'/'对话开始' info notifications (implicit event, no need to show)
- Increase reasoning display limit from 2000 to 3000 chars

BotOps/app.py

@@ -230,7 +230,10 @@ class BotOpsApp(App):
         elif t == "error":
             await self.notify_system(f"❌ {content}", level="error")
         elif t == "info":
-            await self.notify_system(f"ℹ️ {content}")
+            # 过滤掉对话开始这类隐式通知（用户发消息自然知道对话开始了）
+            skip_keywords = ("Conversation started", "对话开始", "🎭")
+            if not any(k in content for k in skip_keywords):
+                await self.notify_system(f"ℹ️ {content}")
         elif t == "command_result":
             await self.notify_system(content)
         elif t == "connection_ack":