fix(ci/mlsysim): strip paper apt-install (drop texlive-science, apt-update)

paper.tex is plain pdflatex with mathpazo (Palatino) + helvet
(Helvetica) + courier — all standard PostScript fonts in
texlive-fonts-recommended. The actual graphics/citation packages it
uses (tikz, pgfplots, subcaption, natbib, hyperref, cleveref,
microtype, fancyhdr, titlesec, etc.) all live in texlive-latex-extra
or texlive-latex-recommended.

A grep for the texlive-science-specific packages (physics, siunitx,
chemnum, chemfig, circuitikz, mhchem, braket, esint, isotope, etc.)
shows ZERO matches in paper.tex. texlive-science was being installed
for ~50-100 MB of dead packages.

Drop it. Also drop apt-get update (defensive against a stale package
cache, but the GHA runner image's apt cache is current within ~1 week
and these texlive packages are stable). Add texlive-latex-recommended
explicitly (was being pulled transitively, but explicit is better).

Expected effect: paper apt-install falls from ~25 min (the recent
2026-05-12 timeout-hitter) to ~3-5 min on a fresh runner. The actual
pdflatex × 3 + bibtex compile is ~30s.

.github/workflows/mlsysim-build-pdfs.yml

@@ -71,16 +71,23 @@ jobs:
         with:
           ref: ${{ inputs.ref || github.ref }}
 
+      # paper.tex is plain pdflatex with mathpazo (Palatino), helvet
+      # (Helvetica), and courier — all standard PostScript fonts in
+      # texlive-fonts-recommended. tikz/pgfplots/subcaption are in
+      # texlive-latex-extra; natbib lives in texlive-latex-recommended;
+      # base math (amsmath/amssymb) ships with the rest. The paper does
+      # NOT use physics/siunitx/chemnum/etc, so texlive-science was
+      # dead weight (~50-100 MB). Drop it and `apt-get update -qq`:
+      # the GHA runner image's apt cache is current within ~1 week
+      # and these packages are stable.
       - name: 📦 Install LaTeX dependencies
         run: |
-          sudo apt-get update -qq
-          sudo apt-get install -y -qq \
+          sudo apt-get install -y --no-install-recommends \
             texlive-latex-extra \
+            texlive-latex-recommended \
             texlive-fonts-recommended \
-            texlive-science \
             poppler-utils \
-            librsvg2-bin \
-            > /dev/null
+            librsvg2-bin
 
       - name: 📄 Build Paper PDF
         working-directory: mlsysim/paper