cuttings: worktrees without the juggling

Field notes

cuttings operates by putting each branch in its own Git worktree and shell, avoiding branch switching in a shared directory. Its disposable mode accepts a command such as `go test ./...`, then removes the temporary worktree after the command exits. The documentation lists pre-built and package-manager installation paths for Linux, macOS, and Windows, along with shell completion and a full command reference.