API listener dies on a single transient accept error; CLI and live handoff unreachable while server and panes keep running #4601

Is this a reproducible bug?

• I confirm this is a reproducible bug, not a feature request, idea, question, contribution proposal, or direction check.
• I reproduced this bug on the version and environment reported below using the exact steps provided.

Current behavior

After the server had been running for ~8 hours, every CLI command started failing with no herdr server is running at ~/.config/herdr/herdr.sock. The server process was still alive (16 panes with shells running), the TUI client socket still worked, and the socket file herdr.sock still existed — but nothing was accepting on it (connecting gives Connection refused).

The server log shows the moment it broke (single line, then normal pane/focus/persist activity continues for hours afterwards):

2026-09-24T09:53:32.862733Z ERROR herdr::api::server: api listener accept failed err=Software caused connection abort (os error 53)

I reproduced the dead-socket state by inspecting the running process: lsof on the server PID showed no listener on herdr.sock, and a direct connect to the socket returned ECONNREFUSED, while herdr status --json reported server not_running.

Expected behavior

A single transient accept error should not permanently remove the API socket. The server should keep serving CLI commands and live handoff until it is intentionally stopped.

Reproduction

1. Start herdr with several panes and let it run.
2. Wait for a transient accept error to hit the API listener (in my case after ~8h of uptime; the log line above is the only signal).
3. Run any CLI command, e.g. herdr status --json → server_not_running; herdr server live-handoff ... → server_not_running, even though the process and panes are alive.

Impact

The server becomes unreachable from the CLI while all panes keep running. Live handoff is impossible, so the only recovery is kill <server-pid>, which terminates every running pane process. I lost 5 active Claude sessions this way.

Environment

• Herdr version: 0.9.1
• Update channel (stable or preview): stable
• Operating system: macOS 15 (Apple Silicon)
• Terminal: Ghostty
• Shell, if relevant: zsh
• Relevant config, if any: default socket paths