Separate window and tab titles in tmux integration
tmux does not distinguish window titles from tab titles because it doesn't know about windows and tabs.
It's useful to have separate titles for them, though.
One option would be to store the window title in the same variable as the affinity. This is subject to races when multiple clients are attached and won't record the title change if no iTerm2 client is attached in integration mode.
Another option would be to extend tmux to record a tab and window title for each tab, plus the time at which each was set. OSC 0, 1, and 2 would need to be supported properly. iTerm2 would need to restore this when attaching. It's hard to imagine how this could be used by plain-old-tmux, though, since it has no notion of windows, so it might be a hard sell to add this to tmux.