fix: stty graceful failure, backend-size TYPE-ERROR safety net

- cl-tty stty calls now use :ignore-error-status t (works in PTY/piped env)
- backend-size wraps in ignore-errors with 80x24 fallback in resize handler
- Both fixes enable TUI to run in environments without full terminal capabilities

lisp/channel-tui-main.lisp

@@ -809,7 +809,9 @@
                 (cl-tty.input:read-event be :timeout 0)
               (cond
                 ((eq type :resize)
-                 (multiple-value-setq (w h) (cl-tty.backend:backend-size be))
+                 (multiple-value-setq (w h)
+                   (or (ignore-errors (cl-tty.backend:backend-size be))
+                       (values 80 24)))
                  (setf prev-fb (cl-tty.rendering:make-framebuffer w h)
                        curr-fb (cl-tty.rendering:make-framebuffer w h))
                  (setf (getf *state* :dirty) (list t t t)))