ChatGPT/Claude Projects are a great way to group files/chats and use them for long-running projects. But seems like there is no way to add/update files in projects. Why?

One of the basic project management needs is to keep track of its stages and generate some artifacts on each stage. Claude can generate artifacts, but can't add them to the project. ChatGPT can't either. Even if you add a markdown file with a simple TODO list, and want to update completed tasks, "projects" can't do it.

Is there a reason for such a limitation? Or am I missing something obvious?