Draw BRD flowcharts with Graphviz
The hand-placed SVG layout struggled with branches and loop-backs, so exports now lay diagrams out with Graphviz (@viz-js/viz, the wasm build). It's an optional dependency - if it can't be installed, or DIAGRAM_RENDERER=builtin is set, the old layout is used instead.
Table sections can carry a diagram now too, and HTML, PDF and Word all render it under the table.