[SandObserver]

Summary

• Reduce the comments in ui/css/tokens.css to the constraints a rule author has to know: the prefix floor, the two accessibility greys, the label and fill limits, the tracking-per-step rule, the font cut rule.
• Drop the historical narrative from those comments (what was removed, what a value used to be, why a duplicate existed).
• Trim docs/design-system.md to the same standard, keeping every table, token name and rule.

Testing
All green. No new coverage; comments and prose only, no declarations changed.

Checklist

• Stays within the project constraints: one container, no runtime dependencies, no build step (see CONTRIBUTING.md).
• Tests added or updated for new logic, and the full suite, lint, and typechecks pass.
• Docs updated if behavior or configuration changed.
• CHANGELOG.md updated under Unreleased if the change is user-visible.