clientIO/joint ? reverse-engineered prompt

Build me a browser based diagramming library and demo app for making flowcharts, process maps, org charts, and simple network style diagrams.

I want users to be able to drag shapes onto a canvas, connect them with lines, edit labels, move things around, zoom in and out, and save and load the diagram as JSON. It should support a few basic shapes like rectangles, circles, text, and images, plus custom shapes, ports on shapes, arrowheads, link labels, and nested groups or containers. Please make it feel polished and interactive, with sensible defaults and enough examples that I can see how to build common diagram types.

If it makes sense, set it up so it works nicely in React too, but keep it framework friendly. Use the current docs online if you need to, and include a handful of realistic demo screens so I can explore the main features right away.