Ports opstool's per-family element colours and its diverging response
scale; RenderStyle.response_scale_colors now also drives the PyVista
force-diagram colouring instead of a hard-coded "coolwarm".
The frame renderer drops the two-trace normal/selected workaround: my
earlier assumption that plotly cannot colour segments individually was
wrong. Scatter3d.line.color accepts an array mapped through a colorscale,
so one trace now carries per-element colours (family + selection) and is
ready to be coloured by response value later.
Attribution recorded in NOTICE per GPLv3 section 5(a)/(b).
Project → plotly.js figure dicts with no Qt/pyvista/plotly import, so
it is unit-tested in the headless job. Mirrors the PyVista renderer's
geometry (grid, nodes, frames, supports, loads, extrusions, local
axes, labels, deformation) while respecting plotly.js's medium:
pixel-sized markers, None-separated line segments, selection as a
second trace (per-segment line colours are impossible), cone traces
for arrows. Pickable traces carry meta.kind + customdata.
