fix: disable flow control (-ixon) for Ctrl+Q, constrain prompt/hint to chat-w

- Added -ixon to stty so Ctrl+Q (XON byte) isn't swallowed by the
  terminal driver and reaches the TUI as :CTRL-Q
- view-input now truncates the prompt (> prefix + visible text) to
  chat-w - 2 characters, and the hint to chat-w characters, so
  neither extends into the sidebar area

passepartout

@@ -412,7 +412,7 @@ LISPEOF
         export MY_TERM_ROWS="${ts%% *}" MY_TERM_COLS="${ts##* }"
         # Set character-at-a-time mode BEFORE SBCL starts
         # (uiop:run-program inside SBCL can't access the terminal)
-        stty -icanon -echo 2>/dev/null
+        stty -icanon -echo -ixon 2>/dev/null
         # Clear stale cl-tty cache to ensure latest backend-size fixes
         find ~/.cache/common-lisp -name "*.fasl" -path "*cl-tty*" -delete 2>/dev/null
         exec sbcl --noinform --load /tmp/tui-load.lisp