Add Phase 1 smoke test

[enricopiovesan]

Purpose

Add a deterministic, CI-friendly smoke test that proves the full Phase 1 path: workflow start → event receipt → final rendered output.

Definition of Done

• Smoke test starts or connects to local Traverse runtime
• Smoke test starts the React app or tests the app boundary
• Verifies: workflow start → event receipt → final rendered output
• Output is concise and CI-friendly
• Exits 0 on pass, exits 1 with diff on fail

Proposed Test Flow

1. Start local Traverse runtime (or stub)
2. Start React app (or invoke app boundary directly)
3. POST start-workflow with fixture input
4. Assert events received: [started, progress, completed]
5. Assert rendered output contains runtime-provided fields (non-empty, not UI-computed)

Dependencies

Depends on #4 (deterministic UI flow).