[209_17] Added separate light and dark mode color schemes for Python

[1sh-repalto]

Follow-up PR for #2553
In the dark theme, the syntax highlighting for languages such as Python is also difficult to see.

Summary

This new approach creates seperate colour schemes for light and dark mode. It also aligns with Mogan's native styling system, allowing for instant theme updates, side-by-side theme support, and better performance.

Developer Document: devel/209_17.md

Issues Found

The previous implementation used a single set of colors for both light and dark modes.

Changes

In TeXmacs/plugins/python/progs/code/python-lang.scm:

• Replaced hardcoded color values in define-preferences with symbolic variable names (e.g., syntax-python-keyword).
• Added a notify-python-pref callback to handle real-time preference updates.
• Simplified the module by removing imperative theme-switching Scheme logic.

In TeXmacs/plugins/python/packages/code/python.ts:

• Defined the default (light) values for all syntax-python-* variables.

In TeXmacs/packages/themes/dark/dark.ts:

• Defined the dark-mode overrides for the same syntax-python-* variables.

How to Test

1. Open Mogan and write some Python code in a code block or session.
2. Toggle between Document -> Theme -> Dark and Document -> Theme -> Plain.
3. Verify that the syntax highlighting colors update instantly and remain legible in both themes.

seperate_dark_color_scheme.mp4

Light Mode

Dark Mode

[Yuki-Nagori]

@1sh-repalto Thank you for your code, I reviewed it and it is correct, but you need to add a test document in tests/tmu/, after that we can merge it!

[1sh-repalto]

Hello @Yuki-Nagori , I have added the test file TeXmacs/tests/tmu/209_17.tmu. Please let me know if further changes are needed. Thanks!

I verified the document loads and renders perfectly by running:
TEXMACS_PATH=$PWD/TeXmacs ./build/linux/x86_64/release/moganstem TeXmacs/tests/tmu/209_17.tmu