registerProfileProvider

为换肤插件显式提供可供客户端使用的档案；UUID 必须匹配请求，URL 仅接受可信的 textures.minecraft.net 地址。 Supplies a client-usable custom profile with the requested UUID and a trusted textures.minecraft.net URL (or null for a default skin).

与图片提供器使用相同的工作线程、3 秒等待和缓存失效规则；图片提供器仍优先决定头像像素。 Uses the same workers, 3-second provider wait and invalidation rules. Image providers retain priority for face pixels; integrations registering both must supply matching skins. Returning null or failing defers to the next profile provider.