Use description environments for labeled lists in 2025a.tex and 2025b.tex

[dbosk]

Context

A review of the new 2026a scenario chapter
(modules/week-8/project/2026a.tex, branch add-2026a-scenario)
converted \item \emph{Label}: … itemize lists to semantic description
environments (commit 0cb2ebe). The same anti-pattern exists in the older
scenario chapters but was out of scope for that review.

Observation

Labeled lists are typeset as \begin{itemize} with manually emphasized
labels instead of \begin{description} with \item[Label]:

• modules/week-8/project/2025a.tex lines 764–770 (side-channel
  mitigations) and 871–876 (upload-receipt consequences)
• modules/week-8/project/2025b.tex lines 973–980 (fallback-code
  protections)

Why it matters

The project's LaTeX conventions call for semantic markup: term–definition
pairs belong in description environments, not visually emulated with
\emph{Label}: in itemize. Fixing this keeps the scenario chapters
consistent with 2026a.tex.

Evidence

grep -n '\\item \\emph{[^}]*}:' modules/week-8/project/2025a.tex \
  modules/week-8/project/2025b.tex

Suggested follow-up

Convert the listed items to \begin{description} with \item[Label],
matching the conversions made in 2026a.tex, and rebuild notes.pdf to
confirm layout.