fix: remove :input :interactive from stty size subprocess

:input :interactive causes uiop to block on /dev/tty in the parent.
stty size queries terminal via ioctl, not stdin — no input
redirection needed.

src/backend/simple.lisp

@@ -27,7 +27,6 @@
           (ignore-errors
             (let* ((out (uiop:run-program '("stty" "size")
                                           :output :string
-                                          :input :interactive
                                           :ignore-error-status t))
                    (parts (and out (uiop:split-string
                                      (string-trim '(#\newline #\space) out)))))