fix(ci/mlsysim): bump build-paper timeout 10 → 30 min

The Latin Modern font swap fixed the slides side of mlsysim-publish-live,
but the parallel build-paper job is now the bottleneck — its 10-min
timeout was hit mid 'Install LaTeX dependencies' on the 2026-05-12 publish
retry, cancelling the whole pipeline (Build & Deploy skipped because
build-paper cancelled).

Same root cause as the earlier slides-side timeout bump (20→40): the
texlive-latex-extra + fonts-recommended + science + poppler-utils
combo can consume the full 10 min in apt-install alone on a fresh
runner. Bump to 30 — gives apt the room it needs without inviting
runaway jobs (real pdflatex build is ~2 min).

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

@@ -57,7 +57,13 @@ jobs:
   build-paper:
     name: '📄 Build Research Paper PDF'
     runs-on: ubuntu-latest
-    timeout-minutes: 10
+    # 10 min was too tight for fresh runners: texlive-latex-extra +
+    # fonts-recommended + science + poppler-utils can consume that
+    # whole budget in apt-install alone (2026-05-12: cancelled mid
+    # install at the 10-min mark). Same root cause as the slides job's
+    # earlier timeout bump — apt is the long pole, not the actual
+    # pdflatex build.
+    timeout-minutes: 30
 
     steps:
       - name: 📥 Checkout