[umpireboulianne-design]

Summary

• Add explicit ARIA landmarks, roles, busy states, and list labels across demo components (AttackDemo.tsx, RoundStatusBadge.tsx, and DemoPage.tsx):
  • RoundStatusBadge exposes role="status" (or role="alert" on error) and aria-busy={state === "loading"}.
  • AttackDemo labels the main attack panel section, marks the Seal-OFF and Seal-ON columns with role="region" and aria-label, sets aria-busy={loading} on the action button, marks errors with role="alert", and labels the step lists (Seal-off attack steps vs Seal-on protection steps).
  • DemoPage labels the sidebar navigation (aria-label="Demo navigation") and mode tablist (aria-label="Demo mode").
• Add apps/web/src/demo/demo-a11y-smoke.test.tsx (imported by trace-health-check.test.ts so pnpm web:test executes it in CI) covering default, loading, error, seal-on, and seal-off states for accessible names, roles, landmarks, and focusable controls.
• Document the accessibility smoke checks in docs/DEMO_SCRIPT.md.

Supply-chain review

• No package scripts or dependencies changed. If changed, explain why below.
• No .vscode/, workflow, or other editor/config file changes. If changed, list them below.
• No lockfile changes. If changed, explain the update below.
• No binary or font asset changes. If changed, list and justify them below.
• I confirm no automatic task (such as preinstall/postinstall) was added.
• I confirm no hidden executable payload (encoded blob, obfuscated command, or unexpected binary) was added.
• Any changed executable or binary was reviewed by a maintainer.

Testing

• node --import tsx --test src/demo/demo-a11y-smoke.test.tsx in apps/web (6/6 tests pass)
• node --import tsx --test src/demo/trace-health-check.test.ts in apps/web (16/16 tests pass)
• node scripts/check-links.js (passes)

Closes #546
Fixes #546