Two issues with sandbox container spawning:
1. PID 1 was `sleep 2h` which doesn't call wait() — every background
process that exited became a zombie (<defunct>), and the process
tool reported them as "running" because zombie PIDs still exist in
the process table. Fix: add --init to docker run, which uses
tini (Docker) or catatonit (Podman) as PID 1 to reap children
automatically. Both runtimes support --init natively.
2. The fixed 2-hour lifetime was arbitrary and sometimes too short
for long agent sessions. Fix: replace 'sleep 2h' with
'sleep infinity'. The idle reaper (_cleanup_inactive_envs, gated
by terminal.lifetime_seconds, default 300s) already handles
cleanup based on last activity timestamp — there's no need for
the container itself to have a fixed death timer.
Fixes#6908.
8254b820ec