Trim the light-dark rationale in the 2.x eds-tokens README to reference ADR-0013

[pomfrida]

Part of #4740 (documentation cleanup, low priority).

The dark-mode section in packages/eds-tokens/README.md (lines ~43–63) was written by the #4864 bug fix and explains internal implementation details (why the published CSS avoids light-dark()) in consumer-facing docs, making dark mode look like a main theme of the package.

Now that ADR-0013 (#5200) is the canonical record of that decision, shorten the README section to a brief note referencing the ADR, and consider the same for the pitfall section in packages/eds-tokens/CLAUDE.md.

Note: a README change only becomes visible on npm with a new 2.x patch, and the manual stable-patch process during beta mode is involved — ride along the next 2.x patch that ships anyway rather than cutting a release for this.

[claude]

These issues look closely related, as they all touch the same light-dark / colour-scheme documentation and decision trail:

• docs: add ADR for attribute-scoped colour-scheme switching over light-dark() #5200 — docs: add ADR for attribute-scoped colour-scheme switching over light-dark() (open): this is ADR-0013 that the README section should reference.
• fix: emit explicit dark-scope rules instead of light-dark() in tokens #4864 — fix: emit explicit dark-scope rules instead of light-dark() in tokens (merged): the change that added the dark-mode rationale text this issue proposes to trim.
• Document the CSS import and colour-scheme changes in the 3.0 migration guide #5203 — Document the CSS import and colour-scheme changes in the 3.0 migration guide (open): sibling documentation-cleanup task covering the same colour-scheme changes.
• 🎨 Refine the EDS Colour & Token System #4740 — 🎨 Refine the EDS Colour & Token System (open): the parent umbrella this work is part of.

This comment was generated by an LLM and may be inaccurate. Please verify that the linked issues are actually relevant.