[Web][W3.1] Define State widget registry and read-only scalar/structured renderers

[code-tc]

Objective

Define the extension and data-binding contract for mapping TinyChain State metadata to UI, then implement read-only scalar, map and tuple renderers.

Scope

Typed widget registry, explicit unsupported-state behavior, SSR-injected versus browser-refreshed state, loading/stale/error/redacted states, developer override points and safe formatting. The client must not infer authority from widget metadata.

Acceptance criteria

• Registry selection is deterministic and overridable without forking.
• Scalar/map/tuple fixtures render equivalently from SSR and browser refresh paths.
• Unsupported, redacted, null, malformed and permission-denied states are visually distinct and non-leaking.
• Serialization round trips and hydration pass tests.
• Gallery and screenshot evidence receives human approval.

Parent: #9

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/state-widgets/registry/**
    - web/src/state-widgets/read/**
    - web/src/ui/gallery/**
    - web/tests/**
    - js/src/**
  prerequisites:
    - "#77"
    - "#78"
    - "TinyChain-Inc/tcv2#53"
  concurrency_group: ui-state-registry
  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