fix: move terminate-process inside let* scope

cat-proc and tty-in were defined by let* but the let* closed at
sleep's third ), putting them out of scope for terminate-process
and read-char. Restructured closing parens so the let* body wraps
the full loop + cleanup.

org/channel-tui-main.org

@@ -1008,7 +1008,8 @@ Event handlers + daemon I/O + main loop.
                                                    nil :bold sel-p)
                            (incf y-off)))))))
                (sleep 0.1)))
-              (uiop:terminate-process cat-proc))
+            (uiop:terminate-process cat-proc)
+            (add-msg :system (format nil "* cat ~a ended *" (uiop:process-info-pid cat-proc))))
          (progn (disconnect-daemon))))
 #+END_SRC