refactor(PageController): implement PageController

packages/page-controller/src/constants.ts

@@ -0,0 +1,16 @@
+/**
+ * Copyright (C) 2025 Alibaba Group Holding Limited
+ * All rights reserved.
+ */
+
+/**
+ * Viewport expansion for DOM tree extraction.
+ * -1 means full page (no viewport restriction)
+ * 0 means viewport only
+ * positive values expand the viewport by that many pixels
+ *
+ * @note Since isTopElement depends on elementFromPoint,
+ * it returns null when out of viewport, this feature has no practical use, only differ between -1 and 0
+ */
+// export const VIEWPORT_EXPANSION = 100
+export const VIEWPORT_EXPANSION = -1