As she treads the cancer treatment labyrinth of hopes and fears, Catherine, Princess of Wales, announced Friday she will make her first public appearance on Saturday since January surgery revealed she had cancer. In March, the princess ended weeks of speculation about her health by announcing in a video posted to social media platform X that she was being treated for cancer. Since then, she has remained very private. On Saturday, the Trooping the Color ceremony is held to mark the king’s official birthday. King Charles, who is also battling cancer, will be there, as will Prince William and Kat…