Epic: WebSocket RMA Infrastructure

[tobiu]

Define and implement the core infrastructure for bidirectional communication between Node.js Agents and Neo.mjs Browser Apps via WebSocket.

Scope:

1. Neo.ai.server.WebSocket: A Node.js server that accepts connections from Browser Apps and Agents.
2. agent-api.json: Schema definition for the API surface exposed by Agents to the Browser.
3. Browser-side Lifecycle: Manage connection/disconnection logic in Neo.main.addon.Remote.
4. Multi-Window Routing: Ensure messages can be routed to specific browser windows (App Instances).
5. Connection Protocol: Define handshake, heartbeat, and reconnection logic.
6. Message Format: Standardize RPC envelope (correlation IDs, timeouts, errors).
7. Performance: <50ms RPC latency target.

Key Constraint:
This infrastructure must support Pattern 2 (Agent Calls Browser), allowing the backend to invoke Neo.worker.App methods as RPCs.

Reference: .github/AGENT_ARCHITECTURE.md