[Experimental] Use jupyter-book 2.0 for building the lectures

[kp992]

Experimental setup for building lectures with jupyter-book 2.0.

This PR is built on top of #345.

[github-actions]

🚀 Deployed on https://688038a10dbee1dd2ed3075b--epic-agnesi-957267.netlify.app

[mmcky]

@kp992 thanks for opening this. Excellent work! It is exciting to see how close we are now.

From my review it looks like there a just a few issues and features we need before launch.

Bugs:

1. LHS TOC menu flickers when using the Home page or a top level Part section. It is like it has an auto-stow feature that is triggering when pages are reloaded. It doesn't look great when pages are refreshed.
2. Code block formatting has too much indentation for Solution blocks

Features:

1. I see a bunch of new export notebooks being added to the yaml headers of each lecture. Do we need to do some development work on supporting the download notebook link in the theme?
2. Is index support on the jb2 / mystmd roadmap?

[mmcky]

CommonMark ipynb Export Support

This commit adds CommonMark notebook export to the JB2 branch, enabling myst build --ipynb to produce notebooks with plain CommonMark markdown cells — compatible with vanilla Jupyter Notebook, JupyterLab (without jupyterlab-myst), and Google Colab.

Changes

24 lecture files — added markdown: commonmark to each export config:

exports:
  - format: ipynb
    markdown: commonmark      # new
    output: exports/<name>.ipynb

New CI workflow (.github/workflows/build-ipynb.yml) — runs in parallel with the existing JB2 workflow:

• Clones QuantEcon/mystmd@myst-to-ipynb and builds from source
• Runs myst build --html and myst build --ipynb using the custom CLI
• Audits all 24 exported notebooks for MyST syntax leaks
• Uploads ipynb exports as build artifacts

How it works

The markdown: commonmark option triggers an AST pre-transform in myst-to-ipynb that converts MyST-specific nodes to their CommonMark equivalents before serialization:

MyST syntax	CommonMark output
:::{note} admonitions	> **Note** blockquotes
Math roles	$E=mc^2$ dollar signs
Math blocks	$$...$$ dollar-dollar
:::{figure} / {image}	
{exercise} / {solution}	Exercise N / Solution blocks
{proof} / theorem	Theorem (Title) blocks
(label)= targets	Stripped
{index} directives	Stripped
+++ block markers	Stripped

Local test results

All 24 notebooks exported successfully with 0 MyST syntax leaks (verified by automated audit script).

Dependencies

This uses the myst-to-ipynb branch on QuantEcon/mystmd which contains 5 commits:

• 79c7be0b — Bug fixes (kernelspec, language_info, log message, block markers)
• f67f1188 — CommonMark serialization mode (~475 lines)
• c1cca05f — Test suite (35 tests across 3 YAML files)
• 2d70076d — Real-world validation fixes (identifier stripping, empty cell filter)
• 2c7fa5d7 — Image directive handler (found during full-project testing)

[mmcky]

@kp992 I have been working on the myst-to-ipynb feature.

Here are a collection of test notebooks: https://github.com/QuantEcon/lecture-python-programming.myst/actions/runs/22381335617 (can download the artifact).

This is looking pretty good I think.