Three lectures render Chinese plot labels as tofu — no matplotlib font configuration

Three lectures set Chinese text on matplotlib figures but carry no font configuration, so matplotlib falls back to DejaVu Sans, which has no CJK coverage. The labels render as tofu — blank rectangles — in a valid PNG, and nothing fails.

Fix

Add the edition's standard block to each, above first plotting use:

FONTPATH = "fonts/SourceHanSerifSC-SemiBold.otf"
mpl.font_manager.fontManager.addfont(FONTPATH)
plt.rcParams['font.family'] = ['Source Han Serif SC']

Note fonts/, not _fonts/ — this edition keeps the asset at lectures/fonts/SourceHanSerifSC-SemiBold.otf and the other 103 configured lectures all use that path.

Context

Not yet visible to readers: this edition last published 2025-11-06 and the breakage is post-dated, so the live site still serves pre-resync content. That is timing, not safety — it ships on the next publish.

Root cause and the recommendation against reverting to usetex are in the program review: project-translation reports/2026-07-24-cjk-font-rendering-review.md. Engine side is action-translation#107 — the resync drops i18n adaptations. A further ~12 lectures here use matplotlib with English labels and no config, which becomes tofu the moment anyone localises a label.

CI cannot currently catch any of this: the missing-glyph warning is raised in the kernel subprocess, so -W never sees it.

Inspect divergence_measures.md, kesten_processes.md, and jv.md, comparing their plotting sections with the 103 lectures that already use the edition’s standard font block. Check the asset at lectures/fonts/SourceHanSerifSC-SemiBold.otf and render the affected figures. Done means all three lectures configure that font before plotting and their Chinese labels render without tofu.