flow in markdown quarto

[moodymudskipper]

For some reason I never got it quite right, but I think I was hoping that the default printing would include the diagram in the doc, I think we might have out = "report" that uses knits::include_graphics() on a temp png file. I don't remember why it was a challenge to recognise that we're knitting and adapt the behavior, there should be an env variable. Let's have another pass on this.