Add Design Tokens concept doc

Author: sarina

source/developers/concepts/design_tokens.rst

@@ -0,0 +1,63 @@
+Design Tokens
+#############
+
+What are Design Tokens?
+***********************
+
+Design tokens are all the values needed to build and maintain a design system —
+spacing, color, typography, object styles, etc. They can represent anything
+defined by the design: color as an RGB value, opacity as a number, spacing as a
+REM value. They are used instead of hard-coded values to provide flexibility and
+uniformity across the application.
+
+By defining style properties as tokens, we can transform the styles into various
+implementations compatible with different platforms or formats (e.g.,
+transforming tokens to CSS variables, CSS utility classes, and eventually
+mobile).
+
+Paragon uses `style-dictionary <https://github.com/style-dictionary/style-dictionary>`_ to build design tokens into CSS variables.
+
+Background & Motivation
+***********************
+
+Design tokens debuted as the primary theming mechanism in the Ulmo release (January 2026), and was available for beta testing in the Open edX Teak release (June 2025).
+
+.. warning::
+   
+   There will be no overlap between the old SCSS-variable theming system and Design Tokens. Site operators must prepare migration strategies in advance.
+
+**Background reading:**
+
+* `Scaling Paragon's styles architecture with design tokens (Confluence) <https://openedx.atlassian.net/wiki/spaces/BPL/pages/3630923811/Scaling+Paragon+s+styles+architecture+with+design+tokens>`_
+* `ADR: design tokens implementation in Paragon <https://github.com/openedx/paragon/blob/master/docs/decisions/0019-scaling-styles-with-design-tokens.rst>`_
+* `November 2024 Open edX meetup presentation slides <https://docs.google.com/presentation/d/1FOSbTUTbbzaBoIDYMa5s32in1uFoYWdoQ-GjKk5IRBo/edit?usp=sharing>`_
+* `Teak design tokens wiki (includes test branches) <https://openedx.atlassian.net/wiki/spaces/BPL/pages/5050499077/Using+Teak+Design+Tokens+branches>`_
+
+Reference Links
+***************
+
+* :ref:`Release note (Ulmo) <Ulmo Design Tokens>`
+* `Paragon tokens source (release-23.x) <https://github.com/openedx/paragon/tree/release-23.x/tokens>`_
+* `Paragon README: Design Tokens section <https://github.com/openedx/paragon/tree/release-23.x?tab=readme-ov-file#design-tokens>`_
+* `brand-openedx (interface definition) <https://github.com/openedx/brand-openedx>`_
+* `brand-openedx: design tokens how-to <https://github.com/openedx/brand-openedx/blob/main/docs/how-to/design-tokens-support.rst>`_
+* `sample-plugin/brand (purple example) <https://github.com/openedx/sample-plugin/tree/main/brand>`_
+* `elm-theme (production example) <https://github.com/edx/elm-theme>`_
+* `tutor-contrib-paragon <https://github.com/openedx/openedx-tutor-plugins/tree/main/plugins/tutor-contrib-paragon>`_
+* `frontend-platform theming docs <https://github.com/openedx/frontend-platform/blob/master/docs/how_tos/theming.md>`_
+* :ref:`OEP-0048: Brand Customization <openedx-proposals:OEP-48 Brand Customization>`
+* `style-dictionary docs <https://amzn.github.io/style-dictionary/#/>`_
+* `W3C Design Tokens Community Group spec <https://tr.designtokens.org/format/#abstract>`_
+* `Confluence: Background/motivation <https://openedx.atlassian.net/wiki/spaces/BPL/pages/3630923811/Scaling+Paragon+s+styles+architecture+with+design+tokens>`_
+* `Confluence: Teak test branches <https://openedx.atlassian.net/wiki/spaces/BPL/pages/5050499077/Using+Teak+Design+Tokens+branches>`_
+* `Paragon design tokens issues <https://github.com/openedx/paragon/issues?q=design+tokens>`_
+* `Paragon CLI issues <https://github.com/openedx/paragon/issues?q=%5BCLI%5D>`_
+
+
+**Maintenance chart**
+
++--------------+-------------------------------+----------------+--------------------------------+
+| Review Date  | Working Group Reviewer        |   Release      |Test situation                  |
++--------------+-------------------------------+----------------+--------------------------------+
+| 2026-03-20   |  Frontend WG                  | Verawood       | Pass                           |
++--------------+-------------------------------+----------------+--------------------------------+

source/developers/concepts/index.rst

@@ -2,7 +2,7 @@ Concepts Home
 #############
 
 .. toctree::
-   :maxdepth: 2
+   :maxdepth: 1
    :glob:
 
    *

source/developers/index.rst

@@ -29,7 +29,7 @@ Open edX Developers
       * :ref:`qs Dev Contributing`
       * :ref:`Tutor QS (Dev)`
       * :doc:`references/running_pr_tests`
-      * :doc:`concepts/hooks_extension_framework`
+      * :doc:`concepts/design_tokens`
 
    .. grid-item-card:: How-tos
       :class-card: sd-shadow-md sd-p-2