[Web][W2.3] Build responsive application shell and navigation patterns

[code-tc]

Objective

Provide a reusable application shell for browser and React Native Web applications without coupling it to a TinyChain product domain.

Scope

Header, primary/secondary navigation, breadcrumb, side panel/drawer, content regions, skip links, status/notification region and authenticated-user slot. Support mobile, tablet and desktop layouts plus deep links and SSR.

Acceptance criteria

• One example application uses only shared shell APIs.
• Navigation order, landmarks, skip links, route focus and mobile drawer behavior pass keyboard/browser tests.
• Hydration and responsive transitions do not duplicate content or lose focus.
• Long labels, localization, RTL, zoom and safe-area behavior are represented.
• Screenshot sets cover all canonical viewports and require human approval.

Parent: #8

Required visual evidence

The draft PR must provide a runnable component-gallery route plus before/after screenshots at 390×844, 768×1024, and 1440×900. Cover light, dark, high-contrast, default, hover, focus-visible, disabled, loading, empty, error, and overflow states applicable to the component. Playwright must exercise keyboard interaction and capture deterministic screenshots. A reviewer other than the implementing agent must approve intentional baseline changes; screenshot generation or a passing pixel threshold is not visual approval.

Tembo execution contract

automation:
  eligible: true
  executor_profile: tembo
  readiness: blocked
  primary_repository: TinyChain-Inc/client
  base_branch: main
  writable_scope:
    - web/src/ui/shell/**
    - web/src/ui/gallery/**
    - web/tests/**
    - web/src/example/**
  prerequisites:
    - "#77"
    - "#78"
  concurrency_group: ui-composites-shell
  required_commands:
    - "cd web && npm ci"
    - "cd web && npm run test:all"
  external_actions: none
  draft_pr_only: true
  completion_authority: human
  visual_validation:
    required: true
    browsers: [chromium]
    viewports: [mobile, tablet, desktop]
    evidence: [component-gallery-url, screenshot-bundle, playwright-report]
    baseline_update_requires: human-visual-approval
    failure_policy: never-auto-accept-diff
  budget:
    size: large
    max_revisions: 3
    max_wall_minutes: 120