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>

web/vite.config.ts

@@ -16,6 +16,18 @@ export default defineConfig({
   server: {
     fs: {
       allow: ['..']
+    },
+    proxy: {
+      '/api': {
+        target: 'http://localhost:8082',
+        changeOrigin: true,
+        ws: true
+      },
+      '/model': {
+        target: 'http://localhost:8082',
+        changeOrigin: true,
+        ws: true
+      }
     }
   }
 })