feat(cursor_manager): 添加鼠标指针动画管理

之后的所有改变鼠标指针动画的行为，都应转移到该类进行处理。

scripts/cursor_manager/cursor_manager.gd

@@ -0,0 +1,38 @@
+## 用于检测与鼠标重合的、[member Area2D.z_index] 最高的 [Area2D]，并根据其状态设置鼠标光标形状。
+class_name CursorManager extends Area2D
+
+
+const CURSOR_ARROW := preload("res://bg/cursor/cursor_arrow.png") ## 鼠标光标为指针时的素材。
+const CURSOR_POINTING_HAND := preload("res://bg/cursor/cursor_pointing_hand.png") ## 鼠标光标为指向时的素材。
+const CURSOR_DRAG := preload("res://bg/cursor/cursor_drag.png") ## 鼠标光标为拖拽时的素材。
+
+
+func _ready():
+	Input.set_custom_mouse_cursor(CURSOR_ARROW)
+	Input.set_custom_mouse_cursor(CURSOR_POINTING_HAND, Input.CURSOR_POINTING_HAND)
+	Input.set_custom_mouse_cursor(CURSOR_DRAG, Input.CURSOR_DRAG)
+
+
+func _process(_delta):
+	self.global_position = get_global_mouse_position()
+
+	# 获取 z_index 最高的 Area2D
+	var top_area: Area2D = null
+	for area in get_overlapping_areas():
+		if top_area == null or area.z_index > top_area.z_index:
+			top_area = area
+
+	if top_area == null:
+		Input.set_custom_mouse_cursor(CURSOR_ARROW)
+	elif top_area is Card:
+		if top_area.is_dragging:
+			Input.set_custom_mouse_cursor(CURSOR_DRAG)
+		else:
+			Input.set_custom_mouse_cursor(CURSOR_POINTING_HAND)
+	elif top_area is CardBase:
+		if top_area.get_card_count() > 0:
+			Input.set_custom_mouse_cursor(CURSOR_POINTING_HAND)
+		else:
+			Input.set_custom_mouse_cursor(CURSOR_ARROW)
+	else:
+		Input.set_custom_mouse_cursor(CURSOR_ARROW)

scripts/cursor_manager/cursor_manager.tscn

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+[gd_scene load_steps=3 format=3 uid="uid://prht3u5pnjls"]
+
+[ext_resource type="Script" path="res://scripts/cursor_manager/cursor_manager.gd" id="1_v3lev"]
+
+[sub_resource type="RectangleShape2D" id="RectangleShape2D_stfy2"]
+size = Vector2(0, 0)
+
+[node name="CursorManager" type="Area2D"]
+script = ExtResource("1_v3lev")
+
+[node name="CollisionShape2D" type="CollisionShape2D" parent="."]
+shape = SubResource("RectangleShape2D_stfy2")