fix: nil guards on w and h in all view functions

Prevents crash when backend-size returns nil for height.
Defaults to 80x24 if dimensions are nil or invalid.

passepartout

@@ -406,9 +406,12 @@ case "$COMMAND" in
   (sleep 3) (finish-output) (uiop:quit 1))))
   (passepartout.channel-tui:tui-main))
 LISPEOF
-        # Export terminal dimensions — bash sets COLUMNS/LINES but
-        # doesn't export them to subprocesses by default.
-        export COLUMNS LINES
+        # Set terminal dimensions from stty — bash's $COLUMNS/$LINES
+        # are often missing or not exported. stty size always works.
+        local ts=$(stty size 2>/dev/null)
+        export COLUMNS="${ts#* }" LINES="${ts% *}"
+        [ -z "$COLUMNS" ] && COLUMNS=80
+        [ -z "$LINES" ] && LINES=24
         # 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