Interactive plotly figures: four different answers across the series, two of them broken

[mmcky]

The style guide has a rule for interactive plotly figures. Nothing in the lecture repos applies it, and the published sites currently show four different behaviours — two of which are broken for readers.

What the style guide says

QuantEcon.manual/manual/styleguide/figures.md endorses plotly figures as "a good way to add interactivity to a lecture", mandates fig.show(renderer="notebook_connected"), and mandates an {only} latex link-back to the website. It also documents the failure mode explicitly: since plotly v6 the default renderer emits only plotly's custom mime type, which jupyter-book and myst-nb cannot render, so the cell output appears as an empty box on the published site.

What the sites actually do

Pattern	Where	Published result
Bare fig.show()	lecture-python-intro/lectures/inequality.md:776	Broken. intro.quantecon.org/inequality.html contains zero Plotly.newPlot — the output div is empty. Line 780 tells the reader the figure "is built using plotly and is available on the website"
Commented out	lecture-python.myst/lectures/back_prop.md:534,614; lecture-python-advanced.myst/lectures/BCG_complete_mkts.md:1198; BCG_incomplete_mkts.md:1274,1638,1689,1750,1780	Absent. Eight figures disabled with # fig.show() will provide interactive plot when running; the published pages render zero plotly
go.FigureWidget	lecture-datascience.myst/lectures/tools/regression.md:650	Works. datascience.quantecon.org/tools/regression.html renders five
fig.show(renderer="notebook_connected") — the mandated form	nowhere	Applied in zero lecture files

The inequality.md defect is mirrored in lecture-intro.zh-cn and lecture-wasm.

Why this wants a sweep rather than a one-line fix

The broken case matters most, because the page promises a figure that is not there. But the eight disabled figures are a decision nobody wrote down, and the one pattern that works is a third mechanism the style guide does not mention. Fixing only inequality.md would leave three answers standing.

Suggested shape: apply the mandated renderer wherever a figure should ship; decide explicitly whether the eight disabled figures should be restored or removed along with their dead code; and reconcile go.FigureWidget with the style guide, either as a sanctioned second pattern or as something to migrate.

Surfaced while evaluating #54.