fix(a2a): trios-agent offline — reconnect + auto-recovery

[gHashTag]

Agent Status Alert

Detected: trios-agent offline for 330 seconds
Last heartbeat: 2026-05-24T11:XX:XXZ
Impact: No A2A message routing, no task acceptance from chat

Steps to resolve:

1. Check trios Swift app status (macOS menu bar)
2. Verify SSE stream connection to BrowserOS Agent Server (:9105)
3. If disconnected → click status bar icon → reconnect
4. Check Console.app for A2A errors

Prevention:

• Auto-reconnect with exponential backoff (current: manual)
• Add registerA2A() retry on network change

Related: Sessions A-G complete, E2E verified. Session H+ pending.