v2.0.4 — Datum grammar in components

Added

• Datum grammar — the signature, now spoken by components. The orange "datum"
  (Construct's reference line for focus / active / current state) was promoted from focus
  rings and bespoke docs CSS into reusable, opt-in component vocabulary in a new
  components/datum.css:
  • .ct-eyebrow — a mono kicker with a leading datum tick, for labelling sections.
  • .ct-datum-scale — a measured reference line (a ruler with minor/major ticks and an
    orange "origin" segment) for section headers.
  • .ct-specs / .ct-spec (+ .ct-spec--origin) — an engineering datasheet for key figures.
  • Card modifiers in card.css: .ct-card--datum (a corner registration mark) and an
    active state (.ct-card--active / [data-state="active"]) that carries the same orange
    leading edge as .ct-list__item and .ct-sidebar, so every active surface reads as one system.

Accessibility

• Eyebrow and spec labels use --color-text-secondary (≥7:1 on every surface across light,
  dark and high-contrast); orange is reserved for non-text edges/ticks (--color-brand-accent,
  ≥3:1 as a graphic object). Default cards and existing aria-selected card behaviour are unchanged.

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Also in this release (post-2.0.4 docs): branded README, community health files
(CODE_OF_CONDUCT, CONTRIBUTING, SECURITY, issue/PR templates), brand assets, and a
datum-grammar demo page.