ncurses had its support written in September 1995. SysV4 curses had support earlier. I haven't been able to point exactly when xterm gained mouse support to send the data to terminal programs, but definitely before September 1995.
It's been a while, I've been using Vim that way for ~5 years now. It's just less well-known, but it works very well!
tmux tab number can be clicked too.
Yeah, I actually switched from MacVim + Terminal to iTerm + tmux + terminal VIM once I realized mouse support existed.
Bonus is that I can work remotely through SSH with that exact same setup!
:set mouse=a
htop also has clickable columns
nano also has mouse support
I feel like I've been living in a terminal cave!
To be honest I don't actually use the feature, so I frequently forget it exists too. :-P
I don't know but Since QBasic since I used it there.
I started using them for my TUI apps in late 1997, so sometime before that.