test: add Playwright accessibility testing POC for Badge and Status Light

Implements automated accessibility testing using two complementary approaches:

1. ARIA Snapshot Testing
   - Captures and validates accessibility tree structure
   - Detects unintended changes to component semantics
   - Serves as living documentation of expected a11y structure

2. aXe Rule Validation
   - Automated WCAG 2.0/2.1 Level A/AA compliance checking
   - Excludes best-practice rules (focused on component testing)
   - Validates color contrast, ARIA attributes, and more

Test Coverage (14/14 passing, ~6s runtime):
- Badge: default, icons, semantic variants, color contrast
- Status Light: sizes (s/m/l), disabled state, color contrast

Key Implementation Details:
- Integrated with existing Storybook stories (no duplication)
- Element visibility waits (reliable, fast)
- WCAG-only scanning (appropriate for isolated components)
- HTML report generation for debugging

Files Added:
- first-gen/playwright.config.ts - Playwright configuration
- first-gen/test/playwright-a11y/aria-snapshots.spec.ts - ARIA tests
- first-gen/test/playwright-a11y/axe-validation.spec.ts - aXe tests
- first-gen/test/playwright-a11y/README.md - Documentation
- RFC_A11Y_TESTING.md - Comprehensive RFC with scaling plan
- README.A11Y.md - Quick start guide

Usage:
  yarn test:a11y       # Run all accessibility tests
  yarn test:a11y:ui    # Open Playwright UI for debugging
  yarn test:a11y:1st   # Run only 1st gen
  yarn test:a11y:2nd   # Run only 2nd gen

Author: cdransf

.gitignore

@@ -137,6 +137,14 @@ chromatic-build-*.xml
 chromatic-diagnostics*.json
 chromatic.config.json
 
+# Playwright test reports (generated)
+first-gen/test/playwright-a11y/report/
+second-gen/test/playwright-a11y/report/
+
+# Playwright test results (generated)
+playwright-report/
+test-results/
+
 # yarn
 .pnp.*
 .yarn/*