[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

We attempted to use the port forward to connect a Slack bridge to the sandbox OpenClaw gateway via WebSocket. The unstable forward caused frequent ECONNRESET errors, forcing us to abandon the WebSocket gateway approach and switch to per-request SSH instead.

Environment

• OpenShell v0.0.13, DGX Spark v7.4.0
• Forward target: port 18789 (OpenClaw gateway inside sandbox)