fix(tmux): increase history-limit to mitigate copy-mode crash

Raise history-limit from 100k to 500k lines to reduce the frequency
of grid_trim_history runs, which are suspected to leave stale pointers
that cause a SIGABRT in grid_free_line when entering copy mode
(tmux/tmux#4888, tmux/tmux#4962). Not a full fix — the upstream bug
in tmux 3.6a remains open — but delays the trigger condition.

Author: ebkn

.tmux.conf

@@ -27,7 +27,7 @@ unbind C-b
 # send prefix to nested tmux (e.g. over SSH) with C-q C-q
 bind C-q send-prefix
 
-set-option -g history-limit 100000
+set-option -g history-limit 500000
 
 # enable mouse
 set-option -g mouse on