Sparse worktrees can be set up through a temporary copy to block tampering

A worktree is a separate working copy of your project that Claude can use. A sparse worktree contains only some of the project's files. When the tengu_vast_muffin switch is on, Claude Code creates a sparse worktree differently:

• It first checks the new worktree's folder and its git folder.
• It prepares the files using a temporary stand-in git folder instead of running a plain checkout inside the worktree.
• It then moves the results into place.

This adds new ways for creation to fail, such as "Failed to checkout sparse worktree: the new worktree's directory or its .git file changed while it was being set up".