verify(voyage): SC1 10-element checklist + Playwright baseline screenshots

Step 31 of v4.3 plan — Wave 7 SC1 authoritative verification:

- docs/sc1-checklist-verification.md: per-element pass/fail med evidens
  (Group A test referanser + manuell side-by-side mot llm-security-
  playground). 8 av 10 PASS bokstavelig, 2 PASS-redef (Element 4
  onboarding-grid -> fleet-grid, Element 6 screenshots-spor -> hooks +
  docs-konvensjon) per scope-guardian Assumptions 21+22 (operator-
  signed-off ved sesjon-start).
- tests/e2e/snapshots/voyage-playground-light.png (1280x900 light theme)
- tests/e2e/snapshots/voyage-playground-dark.png (1280x900 dark theme)
- tests/e2e/snapshots/a11y-baseline.json: WCAG-violations baseline
  (aria-hidden-focus + color-contrast) defer-til-v4.4

Pixel-diff-spec (Step 30) sammenlikner mot baseline med maxDiffPixelRatio
0.02. Wave 7 = VERIFICATION ONLY; HTML FROZEN; faktisk a11y-fix deferred
til v4.4.

plugins/voyage/tests/e2e/snapshots/a11y-baseline.json

@@ -0,0 +1,9 @@
+{
+  "light": {
+    "aria-hidden-focus": 1,
+    "color-contrast": 4
+  },
+  "dark": {
+    "aria-hidden-focus": 1
+  }
+}