Reload tmux config when the server is running

pgrep -x tmux never matched, since the processes are named "tmux: server"
and "tmux: client", so config reloads were silently skipped.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

bin/omarchy-restart-tmux

@@ -2,6 +2,6 @@
 
 # omarchy:summary=Restart tmux if running with the latest configuration
 
-if pgrep -x tmux; then
+if tmux has-session 2>/dev/null; then
   tmux source-file ~/.config/tmux/tmux.conf
 fi