Reset block numbering within worksheets and handouts

[rbeezer]

Reported on pretext-support: numbered blocks (definitions, theorems, etc.) in sibling worksheet or handout divisions don't restart their numbers in HTML, even though the PDF numbers them correctly.

For example, a chapter with two handouts, ten definitions each, produces:

• PDF: 1.1.1–1.1.10, then 1.2.1–1.2.10
• HTML: 1.1.1–1.1.10, then 1.2.11–1.2.20 — the third component never resets

Cause. The two formats number these blocks by different routes. LaTeX uses its own block tcolorbox counter, declared number within=section; since each handout is emitted as a \section, the counter resets per handout. HTML uses the @serial stamped during assembly. In the assembly serial-stamp pass, the $b-terminal test — which decides whether a division opens its own block-numbering scope — listed only the traditional subdivisions (chapter, section, …) and omitted the specialized ones. So a chapter whose children are handouts is misjudged "terminal," opens a single scope, and pools the blocks of all its handouts into one running count. Using sections in place of handouts avoids the bug precisely because section was in the test.

Origin. The $b-terminal predicate was introduced in #2885 (serial numbers for equations and footnotes), where the omission was already present — so equation and footnote numbering inside sibling worksheets/handouts has had the same latent flaw. It surfaced as this report once #2904 (serial numbers for blocks) routed the shared block counter through the same predicate.

Fix. Add the specialized divisions (exercises, worksheet, handout, reading-questions, references, glossary, solutions) to the $b-terminal test, so each opens its own scope and its blocks restart, matching the print output.

Testing. A synthetic two-handout document now numbers 1.2.1–1.2.3 in HTML, matching the PDF. A before/after build of the sample article (via its publication file) shows no numbering changes — only build timestamps differ.

Claude Opus 4.8, acting as a coding assistant for Rob Beezer