shell: Switch to xterm TERM variable

Move any and all display to xterm-256color color variable, to enable
always the same color display.

tmux/.config/tmux/tmux.conf

@@ -24,9 +24,9 @@ set -g renumber-windows on
 set-window-option -g automatic-rename on
 set-option -g set-titles on
 set -g mouse on
-set -s default-terminal $TERM
 # allow truecolor support
-set -as terminal-overrides ",*:Tc"
+set -g default-terminal 'xterm-256color'
+set -ga terminal-overrides ',xterm-256color:Tc'
 # Set Cursor terminal override, so nvim can change cursor style when changing modes
 # more info see nvim, :help tui-cursor-shape
 # LEGACY: this should not be necessary anymore
@@ -42,6 +42,8 @@ setw -g aggressive-resize on
 # No delay for escape key press
 set -sg escape-time 0
 
+# to enable autoread option in neovim
+set-option -g focus-events on
 
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