Teleporting moves your current session into a cloud session, which runs on Anthropic's servers instead of on your computer. Before it starts, Claude Code checks the state of your git branch. It already stopped the move when you had uncommitted changes or commits that were not pushed.
It now also stops when the branch has untracked files. These are files in your folder that git has never been told to track. The message says the cloud session clones the project from the remote copy, so it won't have those files. It suggests you either commit and push them, or set them aside with git stash -u.
A cloud handoff that used to go ahead with stray untracked files will now be refused. You have to deal with those files first, which also means the cloud session is not left silently missing them.