0.25.0 — Panel component; structural group-key derivation

Added

• New Panel component. A bordered, centered stage for showcasing other
  components against a subtle gradient surface. Registered in the catalogue and
  editable in the editor (frame border/radius, stage surface/padding/gap). Props
  are style, an optional minHeight to fix the stage height so it never
  reflows, and a children snippet.
• SideNavigation gains lead and actions snippets. lead renders at
  the top of the rail above the title (e.g. a logo or company name); actions
  renders at the foot of the nav list. Both hide while the rail is collapsed and
  impose no spacing of their own — the consumer controls it.
• New scaffolding exports from @motion-proto/live-tokens/component-editor:
  buildTypeGroupColorTokens, buildTypeGroupFontTokens,
  buildTypeGroupShareableContexts, structuralGroupKey, and the
  TypeGroupConfig type. Custom-component authors can now reach the individual
  pieces of the type-group scaffolding instead of only the bundled
  buildTypeGroupTokens.

Changed

• Group-key derivation is now structural. buildTypeGroupTokens no longer
  infers a token's group from its last dash-segment; it derives the key by
  stripping the component prefix and the variant/state segments declared in the
  new { component, variants } config. All 11 type-group editors were migrated
  to pass this config, and the bespoke SideNavigation/Table workarounds were
  removed. Existing editors' sibling partitions are verified unchanged; this
  matters only for a custom editor that relied on the old last-dash fallback —
  a token with no derivable group now resolves to a solo color token instead of
  being silently grouped.
• bin/check-component now warns (non-fatal) when a component uses a bare font
  helper across multiple slots.

Changed (breaking)

These shift the rendered defaults of shipped components. Consumers who edited
the affected tokens keep their values; unedited tokens fall through to the new
defaults on upgrade.

• Button text and icon scale up. Default text font-size md → lg and icon
  size sm → md across every variant (primary, secondary, outline, success,
  danger, warning).
• Section Divider small variant restyled. Title is now brand-colored and
  center-aligned, the hairline is off by default, title font-size 2xl → 3xl
  at medium (was bold) weight, and the outer padding is removed. The large and
  medium variants are unchanged apart from dropping their space-4 outer
  padding.

Fixed

• CodeSnippet no longer shows a spurious horizontal scrollbar. Added a
  box-sizing: border-box reset so the snippet's own padding and border stay
  inside max-width: 100%. Its code text now uses --text-brand (was
  --text-brand-secondary).

Docs

• Documentation reorganized: the numbered chapter set moved under
  docs/archive/, and the consumer-facing guides (getting-started,
  creating-components, editing-tokens, themes-workflow, 01-overview)
  were rewritten. The demo landing page was restructured (new footer and
  get-started sections; the old "live" section removed).