[Bug]: `openshell forward start --background` process dies silently

[nv-ddave]

Description

openshell forward start 18789 my-assistant --background creates a port forward that frequently dies without warning. openshell forward list shows dead status but no error is logged.

Steps to Reproduce

1. openshell forward start 18789 my-assistant --background
2. Verify: curl http://127.0.0.1:18789/ → HTTP 200
3. Wait 10-30 minutes
4. openshell forward list → shows dead
5. curl http://127.0.0.1:18789/ → connection refused

Expected Behavior

• Background forward stays alive until explicitly stopped
• Auto-reconnects if the connection drops
• Logs the reason for death

Impact

When using the port forward to connect an external client to the sandbox OpenClaw gateway via WebSocket, the unstable forward causes frequent ECONNRESET errors, making WebSocket-based integrations unreliable.

Environment

• OpenShell v0.0.13
• Forward target: port 18789 (OpenClaw gateway inside sandbox)