[Web][W1.3] Implement accessible interactive controls and overlays

[code-tc]

Objective

Implement the interactive primitive layer with consistent pointer, keyboard, focus, disabled, validation and overlay semantics.

Components

Button/IconButton/Link, TextInput/TextArea, Checkbox/Radio/Switch, Select where supportable across targets, Dialog/Popover/Tooltip, Tabs and dismissible feedback. Prefer platform primitives and small composable APIs over a bespoke interaction framework.

Acceptance criteria

• Every control has an accessible name, visible focus, keyboard contract and disabled/read-only behavior.
• Dialog focus trap, return focus, Escape handling and background inertness pass browser tests.
• Validation messages are programmatically associated without announcing on every keystroke.
• Touch targets, contrast, reduced motion and zoom at 200% pass the documented policy.
• SSR/hydration, outside click, nested overlay and unmount cleanup tests pass.

Parent: #7

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/controls/**
    - web/src/ui/overlays/**
    - web/src/ui/gallery/**
    - web/tests/**
  prerequisites:
    - "#76"
  concurrency_group: ui-foundation-controls
  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