Add front end technical implementation details

What does this MR do and why?

For #431276 (closed)

Extracts discussion on the front end technical implementation from the issue to the living documentation for more effective collaboration.

Note: this graph is a rough draft. There are ways to get lines to stop crossing and be less curved, plus get the nodes to appear in a more orderly structure, but it takes tons of fiddling and it would be better to get this in now rather than try to perfect how the lines are drawn.

Please note: Important caveat

This MR is by no means the final word. Moving this into the blueprint is intended to encourage more collaboration and refinement. We should use a bias for action and our iteration value to improve and expand this document.