State/event flow is currently direct and in-process; not automation-friendly

[liannacasper]

Add a simulator observability protocol to decouple tooling from app internals.

1. Introduce snapshot producers in app isolate for:

   • component hierarchy
   • current form metadata
   • network request/response events
   • recorder action stream

2. Serialize as stable payloads as compact DTO objects across bridge.

3. In host isolate, render tooling UI purely from protocol data (no direct references to app Component instances).

4. Add command endpoints for automation:

   • request snapshot
   • trigger screenshot
   • inject simulated input events