Refactor marker management to use child count for occupancy checks; update road management to handle Marker2D types

Scripts/FollowerMarker.cs

@@ -5,23 +5,4 @@ namespace ParasiticGod.Scripts;
 [GlobalClass]
 public partial class FollowerMarker : Marker2D
 {
-    public bool IsOccupied { get; private set; }
-    public Follower FollowerInstance { get; private set; }
-
-    public void PlaceFollower(Follower followerInstance)
-    {
-        if (IsOccupied) return;
-        AddChild(followerInstance);
-        followerInstance.Position = Vector2.Zero;
-        IsOccupied = true;
-        FollowerInstance = followerInstance;
-    }
-
-    public void RemoveFollower()
-    {
-        if (!IsOccupied) return;
-        FollowerInstance.QueueFree();
-        FollowerInstance = null;
-        IsOccupied = false;
-    }
 }