feat: 完成后端处理链路、优化部分提示词

app/actions/registry.py

@@ -4,6 +4,7 @@ from typing import Any
 
 from app.actions.add import AddHandler
 from app.actions.base import BaseActionHandler
+from app.actions.delete import DeleteHandler
 from app.actions.move import MoveHandler
 from app.actions.resize import ResizeHandler
 from app.actions.update import UpdateHandler
@@ -12,6 +13,7 @@ from app.schemas.screen import Screen
 
 # 新增操作时在此注册，未实现的操作明确报错
 ACTION_HANDLERS: dict[str, BaseActionHandler[Any]] = {
+    "delete": DeleteHandler(),
     "add": AddHandler(),
     "move": MoveHandler(),
     "resize": ResizeHandler(),