fix: remove %query-terminal-size completely

The CSI 18t query leaks into the threaded keyboard reader because
the response arrives on stdin after the reader thread starts. The
response bytes get queued as key events and inserted as text into
the TUI input buffer. Removing the query entirely — ioctl is
sufficient for terminal size detection on all modern terminals.

src/backend/simple.lisp

@@ -39,7 +39,6 @@
                  (values (sb-alien:deref winsize 1)
                          (sb-alien:deref winsize 0)))
              (sb-alien:free-alien winsize))))
-      (%query-terminal-size)
       (values 80 24)))
 
 (defmethod backend-write ((b simple-backend) string)