Add streaming support and refactor Chat UI

- Add run_stream method to AgentCore for streaming output
- Add base_url parameter to LLM clients for OpenRouter support
- Add xbot module for new agent implementation
- Refactor Chat.vue into composable + components (ChatHeader, ChatMessage, ChatInput, ChatSidebar, ChatAgentSelector)
- Add ChatStream handler for SSE streaming in Go server
- Add UseXBot field to chat request

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

agent/app/agent/llm/factory.py

@@ -26,7 +26,7 @@ class LLMFactory:
         if provider.lower() == "openai":
             return OpenAILLM(model_name, api_key, base_url)
         elif provider.lower() == "anthropic":
-            return AnthropicLLM(model_name, api_key)
+            return AnthropicLLM(model_name, api_key, base_url)
         else:
             # 默认使用 OpenAI
             return OpenAILLM(model_name, api_key, base_url)