That's a cool idea. I have a similar, but less elegant setup: I just append every single command that I type to a global (synchronized between machines) history

That's a cool idea. I have a similar, but less elegant setup: I just append every single command that I type to a global (synchronized between machines) history file, one file per month, then I use fzf to search through these when I need something (which is plugged into the usual ^R shell binding). Every command I've typed over the past couple of years is accessible immediately that way. It's not scoped by directory though, but I'm not sure I'd personally need that feature.