refactor: restructure to core/ + ui/ with multi-threaded backend

ui/widgets/left_panel.py

@@ -0,0 +1,23 @@
+"""左侧面板"""
+
+from textual.containers import Container
+from textual.app import ComposeResult
+from .message_history import MessageHistory
+from .input_box import InputBox
+
+
+class LeftPanel(Container):
+    """左侧主面板"""
+
+    def compose(self) -> ComposeResult:
+        """构建左侧面板"""
+        yield MessageHistory()
+        yield InputBox()
+
+    def get_message_history(self) -> MessageHistory:
+        """获取消息历史组件"""
+        return self.query_one(MessageHistory)
+
+    def get_input_box(self) -> InputBox:
+        """获取输入框组件"""
+        return self.query_one(InputBox)