v21.12.0

Highlights

• Type-safe variants: @Showcase<T> is now generic. Variant inputs are typed
  as Partial<InputsOf<T>> (signal inputs only, outputs excluded). Existing call
  sites without a generic argument keep working unchanged.
• Header widget API: plugins can contribute pills/badges to the header bar
  (NgPrismPlugin.headerWidgets, start/end slots, lazy loading).
• Library-wide quality scores: coverage and a11y now surface as color-coded
  header pills via manifest.meta. A11y stays a core feature with build-time
  threshold gating (NgPrismConfig.a11y.{ thresholds, reportPath }).
• Plugin schematics: every official plugin ships an ng-add schematic
  (jsdoc, box-model, coverage, figma, perf). New @ng-prism/core/schematics/utils
  subpath exports a config-ast utility plugins use to patch prism.config.ts
  idempotently.
• Keep-alive panels: opt-in PanelDefinition.keepAlive keeps expensive panels
  (e.g. the Figma iframe) mounted across tab switches.

ng-prism (core)

• feat: generic @Showcase<T> for type-safe variant inputs
• feat: header widget extension point + BUILTIN_HEADER_WIDGETS
• feat: PrismManifest.meta / RuntimeManifest.meta carry library-wide plugin
  data from build to runtime
• feat: a11y build-time pipeline reads a11y-report.json and hard-fails the
  build on threshold violations
• feat: keep-alive panels survive tab switches
• feat: prefer styleguide pages over components in the default route
• feat: config-ast utility + schematics/utils subpath export
• feat: ng-add installs highlight.js + ngx-highlightjs
• fix: variant-ribbon prev/next controls stay visible, active tab auto-scrolls
  into view

Plugins

• plugin-coverage: configurable thresholds per metric; coverage total surfaces
  as header badge via onManifestReady
• plugin-jsdoc: ng-add schematic; descriptions and @example blocks now render
  as Markdown with syntax-highlighted code (bumps plugin to 21.13.0-beta.0)
• plugin-figma: ng-add schematic (with optional-peers hint); embed iframe no
  longer reloads on panel switch (keep-alive)
• plugin-box-model, plugin-perf: ng-add schematics

Refactors & build

• refactor(ng-prism): remove built-in ng-prism-audit-a11y CLI — consumers
  produce a11y-report.json themselves (same pattern as coverage-summary.json);
  playwright and axe-core peerDeps dropped
• chore(publish): beta release flow (--tag beta, prerelease GH releases),
  promote beta → stable, plugin peer-dep sync on bump
• build(ng-prism): exclude __mocks__ from lib build
• fix(ci): ng-prism:test now depends on plugin-jsdoc:build
• docs: ng-add guide for plugins, ADR for plugin schematics architecture,
  @Showcase<T> + InputsOf<T> reference