feat: add nearby social interactions

_Core/utils/InteractionAnchor.gd

@@ -0,0 +1,14 @@
+class_name InteractionAnchor
+extends RefCounted
+
+# 所有交互距离与地图标记共用的世界锚点。
+# Area2D 优先使用实际 CollisionShape2D 的中心，避免脚本节点原点与碰撞区域有偏移时
+# 出现“能交互的位置”和白圈不一致的问题。
+static func get_position(node: Node2D) -> Vector2:
+	var area: Area2D = node as Area2D
+	if area != null:
+		for child: Node in area.get_children():
+			var collision_shape: CollisionShape2D = child as CollisionShape2D
+			if collision_shape != null and not collision_shape.disabled and collision_shape.shape != null:
+				return collision_shape.global_position
+	return node.global_position