feat(ghostty): add tmux session launcher script

dot_local/bin/executable_ghostty-tmux

@@ -0,0 +1,23 @@
+#!/bin/bash
+# Ghostty's `command`: every Ghostty window gets its own tmux session, never
+# a mirror of another window's. Reclaim the oldest detached session (left by
+# a closed window, or restored by tmux-continuum after a reboot) so closed
+# windows don't pile up sessions; otherwise start a new one. The first window
+# after boot starts the server, which is what triggers continuum's restore.
+# ponytail: two windows opened in the same instant can claim the same detached
+# session; take a lock (flock) here if that ever bites.
+#
+# The session's @tab-bg is set to Ghostty's own background (its theme, not
+# Omarchy's), so the tab arrows tmux paints in that color match the window.
+
+oldest=$(tmux list-sessions -f '#{==:#{session_attached},0}' \
+    -F '#{session_created} #{session_name}' 2>/dev/null | sort -n | head -1 | cut -d' ' -f2-)
+
+bg=$(ghostty +show-config 2>/dev/null | sed -n 's/^background = //p')
+set_bg=()
+[[ -n $bg ]] && set_bg=(\; set-option @tab-bg "$bg")
+
+if [[ -n $oldest ]]; then
+    exec tmux attach-session -t "=$oldest" "${set_bg[@]}"
+fi
+exec tmux new-session "${set_bg[@]}"