feat(ms-ai-architect): release v1.9.0 with playground v3 + screenshot suite

Version bump: v1.8.0 -> v1.9.0 (minor — plugin API surface unchanged).

Version sync:
- .claude-plugin/plugin.json (canonical), README.md badge,
  CHANGELOG.md (full v1.9.0 entry with playground v3 architecture,
  validation suite, A11Y artifacts, SemVer rationale),
  marketplace root README.md listing.

Screenshot suite (new):
- scripts/screenshots/capture-playground.py — Playwright Python automation
  that opens playground from file://, populates __store with Statens vegvesen
  ANPR demo data, navigates each surface, paste-imports fixtures, scrolls to
  the relevant report-slot, and saves viewport screenshots.
- 6 PNG screenshots in playground/screenshots/ covering: onboarding (18/18
  filled), home (3 projects), catalog (24 commands across 5 expansion groups),
  classify pyramid (high-risk Annex III), ROS 5x5 matrix + 7-dim radar,
  cost P10/P50/P90 distribution.

Doc updates (3 levels per repo policy):
- Plugin README: new "Screenshots" subsection embeds all 6 with description
  columns, plus reproduce command.
- Plugin CLAUDE.md: new "Screenshot-suite (v1.9.0)" subsection documenting
  the automation, demo-state seeding, and re-run trigger conditions.
- Marketplace root README: ms-ai-architect listing now mentions the
  screenshot suite + reproduce command.

Reproduce screenshots: python3 scripts/screenshots/capture-playground.py.

Notes:
- Light-mode tokens are not in the vendored design-system yet. The toggle
  swaps data-theme + label correctly (Step 13 mechanics intact), but the
  CSS palette only ships dark. Captured dark-mode only; light-mode capture
  re-enables when shared/playground-design-system gains [data-theme="light"]
  overrides.
- Local CSS fix in playground HTML: added `[hidden] { display: none !important; }`
  in the inline app-shell <style> block. The vendored .error-summary rule
  sets display: flex which overrode HTML's [hidden] default, leaking the
  onboarding error banner on cold start. Plugin-local for now; a proper
  fix belongs in shared/playground-design-system/components-tier3.css.

Verified post-bump:
- bash tests/validate-plugin.sh -> 215/215 PASS
- bash tests/run-e2e.sh --playground -> 240/240 PASS

plugins/ms-ai-architect/playground/ms-ai-architect-playground.html

@@ -36,6 +36,11 @@
        Kompakt med vilje — ingen komponent-CSS skal duplikeres her. -->
   <style>
     main#app { min-height: 100vh; padding: 0; }
+
+    /* Hidden-attribute respekt. Vendored .error-summary, .modal-backdrop osv.
+       setter eksplisitt display, som overstyrer HTMLs default [hidden] {display:none}.
+       Globalt override slik at hidden-attributt faktisk skjuler elementet. */
+    [hidden] { display: none !important; }
     .app-shell { max-width: 1200px; margin: 0 auto; padding: var(--space-6) var(--space-5); }
     .app-shell--wide { max-width: 1400px; }