fixes for mksh tmux

tmux/tmux.conf

@@ -8,11 +8,21 @@ set -s escape-time 0
 set -g detach-on-destroy on
 set -g destroy-unattached off
 
+# Keep the server alive with zero sessions. Grouped sessions share "main"'s
+# window list, so closing the last window empties "main" too; with the default
+# `exit-empty on` that killed the whole server out from under every other
+# attached client. The client command below rebuilds "main" on next connect.
+set -s exit-empty off
+
 # bare `tmux` (no subcommand, e.g. from mkshrc's auto-attach) gets its own
 # session grouped with "main" - shared panes/windows, independent per-client
 # current-window navigation. Self-cleans on detach via destroy-unattached.
-new-session -d -s main
-set -g default-client-command "new-session -t main ; set-option destroy-unattached on"
+#
+# `new-session -A -d -s main` is a no-op when "main" exists and recreates it
+# detached when it does not. It is one tmux command, so it is ordered before
+# the `-t main` group join - unlike if-shell/run-shell, which are not.
+new-session -A -d -s main
+set -g default-client-command "new-session -A -d -s main ; new-session -t main ; set-option destroy-unattached on"
 # set -g default-terminal "screen-256color"
 set -g default-terminal "tmux-256color"
 set -g history-limit 50000
@@ -23,7 +33,6 @@ set -g set-titles-string "#W #T"
 set -g display-time 8000
 set -g status-interval 2
 # set -g set-remain-on-exit off
-set -g terminal-overrides 'xterm*:smcup@:rmcup@'
 set -g window-size latest
 set-option -sa terminal-overrides ',screen-256color:RGB'
 set-option -sa terminal-overrides ',st-256color:RGB'
@@ -38,7 +47,6 @@ set-option -sa terminal-overrides ',foot:RGB'
 # keybinds
 unbind-key -a
 
-set -g default-terminal "xterm-256color"
 
 # set-option -ga terminal-overrides ',xterm-256color:Tc
 set-option -sa terminal-features ',xterm-256color:RGB'
@@ -122,7 +130,6 @@ setw -g window-status-current-format '#[fg=black]>#[fg=yellow]#W'
 
 # fix ncurses crash
 set -as terminal-overrides ',st*:Ss@'
-set-option -sa terminal-overrides ",xterm*:Tc"
 # Undercurl
 # set -g default-terminal '${TERM}'
 set -as terminal-overrides ',*:Smulx=\E[4::%p1%dm'  # undercurl support