feat(ai): add LaTeX typesetting stack (PR 3/5)

Add TeXLive packages for PDF generation from Org-mode and LaTeX documents:
- texlive-latex-base: Core LaTeX packages
- texlive-latex-extra: Additional LaTeX packages
- texlive-fonts-recommended: Recommended fonts
- texlive-xetex: XeTeX engine for Unicode support
- texlive-science: Science/math packages

Depends on PR #7 and #8

ai/Dockerfile

@@ -2,15 +2,26 @@ FROM ghcr.io/astral-sh/uv:0.11.6-python3.13-trixie@sha256:b3c543b6c4f23a5f2df228
 FROM tianon/gosu:1.19-trixie@sha256:3b176695959c71e123eb390d427efc665eeb561b1540e82679c15e992006b8b9 AS gosu_source
 FROM debian:13.4
 
+# Disable Python stdout buffering to ensure logs are printed immediately
 ENV PYTHONUNBUFFERED=1
+
+# Store Playwright browsers outside the volume mount so the build-time
+# install survives the /opt/data volume overlay at runtime.
 ENV PLAYWRIGHT_BROWSERS_PATH=/opt/hermes/.playwright
 
+# Install system dependencies in one layer, clear APT cache
+# tini reaps orphaned zombie processes (MCP stdio subprocesses, git, bun, etc.)
+# that would otherwise accumulate when hermes runs as PID 1. See #15012.
 RUN apt-get update && \
     apt-get install -y --no-install-recommends \
         build-essential nodejs npm python3 ripgrep ffmpeg gcc python3-dev libffi-dev procps git openssh-client docker-cli tini \
-        curl poppler-utils imagemagick && \
+        curl poppler-utils imagemagick \
+        chromium xvfb fonts-noto-color-emoji fonts-unifont fonts-liberation fonts-ipafont-gothic fonts-wqy-zenhei fonts-tlwg-loma-otf fonts-freefont-ttf \
+        libasound2t64 libatk-bridge2.0-0t64 libatk1.0-0t64 libatspi2.0-0t64 libcairo2 libcups2t64 libdbus-1-3 libdrm2 libgbm1 libglib2.0-0t64 libnspr4 libnss3 libpango-1.0-0 libx11-6 libxcb1 libxcomposite1 libxdamage1 libxext6 libxfixes3 libxkbcommon0 libxrandr2 \
+        texlive-latex-base texlive-latex-extra texlive-fonts-recommended texlive-xetex texlive-science && \
     rm -rf /var/lib/apt/lists/*
 
+# Non-root user for runtime; UID can be overridden via HERMES_UID at runtime
 RUN useradd -u 10000 -m -d /opt/data hermes
 
 COPY --chmod=0755 --from=gosu_source /gosu /usr/local/bin/
@@ -18,6 +29,9 @@ COPY --chmod=0755 --from=uv_source /usr/local/bin/uv /usr/local/bin/uvx /usr/loc
 
 WORKDIR /opt/hermes
 
+# ---------- Layer-cached dependency install ----------
+# Copy only package manifests first so npm install + Playwright are cached
+# unless the lockfiles themselves change.
 COPY package.json package-lock.json ./
 COPY web/package.json web/package-lock.json web/
 
@@ -26,16 +40,26 @@ RUN npm install --prefer-offline --no-audit && \
     (cd web && npm install --prefer-offline --no-audit) && \
     npm cache clean --force
 
+# ---------- Source code ----------
+# .dockerignore excludes node_modules, so the installs above survive.
 COPY --chown=hermes:hermes . .
 
+# Build web dashboard (Vite outputs to hermes_cli/web_dist/)
 RUN cd web && npm run build
 
+# ---------- Permissions ----------
+# Make install dir world-readable so any HERMES_UID can read it at runtime.
+# The venv needs to be traversable too.
 USER root
 RUN chmod -R a+rX /opt/hermes
+# Start as root so the entrypoint can usermod/groupmod + gosu.
+# If HERMES_UID is unset, the entrypoint drops to the default hermes user (10000).
 
+# ---------- Python virtualenv ----------
 RUN uv venv && \
     uv pip install --no-cache-dir -e ".[all]"
 
+# ---------- Runtime ----------
 ENV HERMES_WEB_DIST=/opt/hermes/hermes_cli/web_dist
 ENV HERMES_HOME=/opt/data
 ENV PATH="/opt/data/.local/bin:${PATH}"