[JS][J4] Validate canonical WASM Library flow and cross-runtime parity

Objective

Provide and test the supported JavaScript flow for loading/installing and invoking a signed WASM-backed TinyChain Library in Node and an actual browser.

Scope

Artifact plus immutable manifest/dependency lock; route/export mapping; approved browser host imports; install/invoke/inspect lifecycle; actual-browser tests; cross-language fixtures and explicit backend-blocked matrix rows.

Acceptance criteria

• One example artifact follows the canonical publication and identity contract.
• Node and browser run the same supported Library scenario through their respective adapters.
• Undeclared imports, substituted artifact, forged context and arbitrary network attempts fail closed.
• JS/Python/Rust fixtures agree for every implemented row.
• Playwright runs the browser/WASM path rather than Node emulation.
• CI retains structured results and redacted diagnostics.

Parent: #74

Tembo execution contract

automation:
  eligible: true
  executor_profile: tembo
  readiness: blocked
  primary_repository: TinyChain-Inc/client
  base_branch: main
  writable_scope:
    - js/src/**
    - js/tests/**
    - web/src/**
    - web/tests/**
    - web/public/**
    - js/ROADMAP.md
  prerequisites:
    - "#86"
    - "#87"
    - "TinyChain-Inc/tcv2#52"
    - "TinyChain-Inc/tcv2#54"
    - "TinyChain-Inc/tcv2#56"
  concurrency_group: js-wasm-parity
  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: false
    evidence: []
  budget:
    size: large
    max_revisions: 3
    max_wall_minutes: 120

Check prerequisites #86, #87 and the listed tcv2 issues before working in js/src, js/tests, web/src, web/tests, and web/public. Run cd web && npm ci followed by npm run test:all to establish the current state. Done means the canonical artifact flow passes in Node and a real browser, fixtures agree across languages, blocked rows and redacted CI results are retained, and the listed rejection cases fail closed.