Fix: "tmux gets weird on splits"

microsoft/terminal#6987

tmux/.config/tmux/tmux.conf

@@ -37,6 +37,7 @@ setw -g aggressive-resize on
 # more colors and themes
 set -as terminal-overrides ',*:Smulx=\E[4::%p1%dm'  # undercurl support
 set -as terminal-overrides ',*:Setulc=\E[58::2::%p1%{65536}%/%d::%p1%{256}%/%{255}%&%d::%p1%{255}%&%d%;m'  # underscore colours - needs tmux-3.0
+set -ag terminal-overrides ',*:cud1=\E[1B' # redraw?
 set -g message-style bg="colour0",fg="colour3"
 set -g pane-active-border-style fg="colour8"
 set -g pane-border-style fg="colour8"