Upgrade the base image to Debian 13 Trixie

[pytooling-claude]

Changes

• The base image moves from python:3.14-slim-bookworm to python:3.14-slim-trixie - Debian 13 Trixie. Pipeline.yml sets base_image_os_version="13" and base_image_os_codename="Trixie"; everything else derives from those two variables, including the MiKTeX apt distribution.
  • MiKTeX's apt repository carries trixie since 2026-05, currently at 26.5-trixie1 - the same MiKTeX version as 26.5-bookworm1, so the distribution changes and the TeX distribution does not.
  • Every Debian package in Base.packages, Common.packages and Sphinx.packages resolves on Trixie. nodejs moves from 18.x to 20.x, which @mermaid-js/mermaid-cli requires anyway.

Bug Fixes

• Dockerfile reads its MIKTEX_SRC_REPO argument. The apt sources line hardcoded bookworm, while the argument was declared twice, passed by Pipeline.yml on every build from miktex_source_repository, and then ignored - so the MiKTeX distribution could not follow the base image. It is derived from base_image_os_codename now, which makes the next upgrade a one-variable change.

Documentation

• README.md names Debian 13.x Trixie as the base.

Known Issues

• The trixie distribution of the MiKTeX repository holds only 26.2 and 26.5, against eleven versions for bookworm. Pinning an older MiKTeX is therefore not possible on Trixie.

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Related Issues and Pull-Requests

• Follows v1.5.1 #31 (v1.5.1).
• Verified outside the pipeline: this container is Debian 13.6 Trixie, and miktex 26.5-trixie1 from the trixie distribution installs the 130 packages of Common.list plus Sphinx.list with mpm and compiles pyTooling's pyTooling.tex to PDF without a missing file.
• Promote images to their official tags only after the checks pass #28 covers the risk of this change: the image is built, pushed and tested as ci-<short sha>, and the official tags are moved onto it only after the tests pass - a broken Trixie build cannot replace pytooling/miktex:dev or :latest.