Clarify design system token guidance

[urumi-ai-sandbox]

Summary

Clarified how the design system tokens are documented so it’s clearer where updates should be made. This helps ensure future visual tweaks stay synchronized between the reference and implementation.

Changes

• Documentation: Adjusted wording in the Design System guide to point to the implementation tokens file and remind to update both references together.

Testing

• Previewed the running site in the builder
• Reviewed the diff

Risks

• Low risk — isolated change.