- BackgroundManager.shutdown() now aborts all running child sessions via
client.session.abort() before clearing state, preventing orphaned
opencode processes when parent exits
- Add onShutdown callback to BackgroundManager constructor, used to
trigger TmuxSessionManager.cleanup() on process exit signals
- Interactive bash session hook now aborts tracked subagent opencode
sessions when killing tmux sessions (defense-in-depth)
- Add 4 tests verifying shutdown abort behavior and callback invocation
Closes#1240
b4973954e3