docs: Studio's PDF export needs LaTeX, in AGENTS.md and Dockerfile.base too

AGENTS.md ("What we DON'T install") and two comments in Dockerfile.base's
typst block still said pi-studio's PDF export uses typst. Same correction
as 77929b7 for the README. AGENTS.md also warns maintainers not to ship
ENV PANDOC_PDF_ENGINE=typst, since pi-studio's LaTeX header is printed as
page text under typst while pandoc exits 0.

Corrects 77929b7: "texlive-xetex alone is not enough" holds only with
--no-install-recommends. With apt's defaults, texlive-xetex (and the old
AGENTS recipe, texlive-xetex texlive-latex-recommended: the same set) works,
but installs 202 packages / 1053 MB including systemd, D-Bus and a JRE.
The README recipe (4 packages, --no-install-recommends) is 37 / 491 MB.
All three recipes measured from the image's 401 packages on v1.11.2 +
pi-studio 0.10.1, checking the exported page, not only the exit code.

Dockerfile.base changes are comments only, but base_tag hashes the whole
file; the next release rebuilds the base anyway.

AGENTS.md

@@ -354,14 +354,24 @@ deprecated artifacts (to be removed in opencode-devbox v2.0.0).
 
 ## What we DON'T install (and why)
 
-- **No texlive** (~600 MB–1 GB). PDF export from pandoc / pi-studio works
+- **No texlive** (~0.5–1 GB). The base ships **`typst`** (~30 MB static
-  out of the box via **`typst`** (~30 MB static binary), which the base ships
+  binary) as a PDF engine for pandoc, so
-  as the pandoc PDF engine (`pandoc --pdf-engine=typst`) — small enough to live
+  `pandoc doc.md --pdf-engine=typst -o doc.pdf` works out of the box. That
-  in base rather than a dedicated `:latest-studio-tex` variant. We don't bake in
+  covers the common Markdown→PDF case, small enough to live in base rather
-  a full TeX Live: it's heavy and typst covers the common Markdown→PDF case.
+  than in a dedicated `:latest-studio-tex` variant. Callers must ask for
-  Users needing LaTeX-exact output can install the higher-fidelity fallback on
+  typst: pandoc's own default engine is `pdflatex`, which is not installed.
-  demand: `sudo apt-get install texlive-xetex texlive-latex-recommended` (then
+  **pi-studio's PDF export (`/studio-pdf`, `studio_export_pdf`) does not use
-  `pandoc --pdf-engine=xelatex`).
+  typst.** It runs pandoc with `$PANDOC_PDF_ENGINE`, defaulting to `xelatex`,
+  so in this image it fails with `xelatex not found`. Do not "fix" that with
+  `ENV PANDOC_PDF_ENGINE=typst`. pi-studio adds its own LaTeX header to the
+  document, and typst prints that header as page text while pandoc exits 0.
+  That ENV only becomes a fix once pi-studio stops sending its LaTeX header
+  to non-LaTeX engines. Until then, users who need Studio's PDF export, or
+  LaTeX output, install TeX Live on demand with the recipe in README
+  "PDF export from Studio needs LaTeX" (37 packages, ~490 MB with
+  `--no-install-recommends`). A plain `sudo apt-get install texlive-xetex`
+  also works, but its recommends make it 202 packages and ~1 GB, including
+  systemd and a Java runtime.
 - **pi-studio** ships in the `:latest-studio` variant (since v1.1.0),
   vendored to `/opt/pi-studio` and registered at container start via
   `pi install /opt/pi-studio` (see Dockerfile.variant `INSTALL_STUDIO`).

CHANGELOG.md

@@ -84,15 +84,24 @@ base** rather than reusing `base-6f3b20266de1`.
     (unless the document sets `header-includes`). Under typst, pandoc exits
     0 and prints that header as text above the first heading. Seen in the same PDF through two renderers, MuPDF and
     Chromium.
-  - **`texlive-xetex` alone, which the README offered as the fallback, is
+  - **`texlive-xetex`, the README's old fallback, works but is twice the
-    not enough.** The export then still lacks `lmodern.sty`, `ulem.sty`
+    size it needs to be.** Installed with apt's defaults it pulls in its
-    and the `pzdr` font. Adding `lmodern texlive-plain-generic
+    recommends: 202 packages and 1053 MB, including systemd, D-Bus and a
-    texlive-fonts-recommended` makes it work: 37 packages and 491 MB
+    Java runtime (`openjdk-21-jre-headless`, 194 MB). The same 202 come from
-    installed, after `apt-get update`. Measured on v1.11.2 with pi-studio
+    the old `AGENTS.md` recipe, `texlive-xetex texlive-latex-recommended`.
-    0.10.1. The exported page was looked at, not only its exit code.
+    With `--no-install-recommends`, `texlive-xetex` alone is not enough:
+    the export then lacks `lmodern.sty`, `ulem.sty` and the `pzdr` font.
+    The README's recipe adds the three packages that provide them,
+    `lmodern texlive-plain-generic texlive-fonts-recommended`, and comes to
+    37 packages and 491 MB, after `apt-get update`. Each recipe was
+    measured from the image's own 401 packages on v1.11.2 with pi-studio
+    0.10.1, and the exported page was looked at, not only its exit code.
 
-  The same claim also appears in `AGENTS.md` ("What we DON'T install") and
+  The same claim is corrected in `AGENTS.md` ("What we DON'T install"),
-  in comments in `Dockerfile.base`. Neither is changed here.
+  which now also warns against `ENV PANDOC_PDF_ENGINE=typst`, and in two
+  comments in `Dockerfile.base`'s typst block. `base_tag` hashes all of
+  `Dockerfile.base`, comments included, so this changes the base hash too.
+  The base is rebuilt in the next release anyway (above).
 
 ## v1.11.2 — 2026-10-14
 

Dockerfile.base

@@ -822,12 +822,16 @@ RUN ARCH=$(case "${TARGETARCH}" in amd64) echo "x86_64" ;; arm64) echo "aarch64"
 
 # ── typst — lightweight PDF engine for pandoc (Markdown→PDF) ─────────
 # pandoc (apt-installed above) is only a front-end; rendering PDF needs a
-# back-end engine. Rather than a ~600 MB TeX Live install, we ship typst:
+# back-end engine. Rather than a ~0.5–1 GB TeX Live install, we ship typst:
-# a single ~30 MB static Rust binary with no LaTeX dependency. pi-studio's
+# a single ~30 MB static Rust binary with no LaTeX dependency. Callers must
-# PDF export (studio_export_pdf) and pandoc invocations use it via
+# ask for it with `pandoc --pdf-engine=typst`, because pandoc's own default
-# `pandoc --pdf-engine=typst`. A fuller TeX Live remains the higher-
+# engine is pdflatex, which is not installed. pi-studio's PDF export
-# fidelity fallback for anyone who needs LaTeX-exact output (not shipped
+# (studio_export_pdf, /studio-pdf) does NOT use typst. It runs pandoc with
-# here — install on demand or in a future variant).
+# $PANDOC_PDF_ENGINE, defaulting to xelatex, so it fails with "xelatex not
+# found". Setting PANDOC_PDF_ENGINE=typst is not a fix: pi-studio adds its
+# own LaTeX header, and typst prints that header as page text while pandoc
+# exits 0. TeX Live is not shipped here; README "PDF export from Studio needs
+# LaTeX" has the on-demand recipe (~490 MB).
 #
 # Follows the `latest` GitHub-release convention (like tealdeer/uv/bat).
 # typst ships a `.tar.xz` asset (hence xz-utils in the apt layer above)
@@ -839,7 +843,8 @@ RUN ARCH=$(case "${TARGETARCH}" in amd64) echo "x86_64" ;; arm64) echo "aarch64"
 # document font to an empty tuple (`font: ()`), so a naked
 # `pandoc --pdf-engine=typst` fails with "font fallback list must not be empty"
 # unless the caller passes `-V mainfont=...`. We default it to Libertinus Serif
-# (typst's own bundled default font) so PDF export works out-of-the-box.
+# (typst's own bundled default font) so a naked `pandoc --pdf-engine=typst`
+# works out of the box.
 ARG TYPST_VERSION=latest
 RUN ARCH=$(case "${TARGETARCH}" in amd64) echo "x86_64" ;; arm64) echo "aarch64" ;; *) echo "x86_64" ;; esac) && \
     V="${TYPST_VERSION}" && \

README.md

@@ -380,10 +380,13 @@ There are two ways out:
     texlive-xetex lmodern texlive-plain-generic texlive-fonts-recommended
   ```
 
-  `texlive-xetex` on its own is not enough. Studio's export then still lacks
+  The image starts with an empty package index, so run `apt-get update`
-  `lmodern.sty`, `ulem.sty` and the `pzdr` font, which come from the other
+  first. With `--no-install-recommends`, `texlive-xetex` on its own is not
-  three packages. The image starts with an empty package index, so run
+  enough: Studio's export then lacks `lmodern.sty`, `ulem.sty` and the `pzdr`
-  `apt-get update` first. (Measured on v1.11.2 with pi-studio 0.10.1.)
+  font, which the other three packages provide. A plain
+  `sudo apt-get install texlive-xetex` also works, but its recommended
+  packages make it 202 packages and about 1 GB, including systemd, D-Bus and
+  a Java runtime. (Measured on v1.11.2 with pi-studio 0.10.1.)
 
 ### Generating a PDF with pandoc + typst