Host shutdown save

Sub-features

logind PrepareForShutdown, the delay inhibitor, resume metadata in the snapshot, retry when login1 is missing or restarted, and inhibitor release on ordinary server shutdown.

How to get to it (user POV)

Shut down or restart the Linux host while a workspace is live. After the next server start, resumable panes still have their session id and resume command. Nothing in the GUI calls this path.

Driving it with real IPC

Run cargo test -p signaltty-server --test logind. The tests start a private dbus-daemon and a fake org.freedesktop.login1. They never contact the host bus and never power off the machine. A true signal or an already-true PreparingForShutdown must write snapshot.json before the inhibitor peer sees EOF. A false signal, a denied inhibit, a missing name and a replaced service must leave the server up until a real shutdown, and server.shutdown must close the inhibitor.

Gotchas

The GUI probes do not cover this. A green workspace test says nothing about the inhibitor. Power loss and SIGKILL can still skip the save. The shared test server and the QA scripts set SIGNALTTY_LOGIND=0; only --test logind opts in, and only against its private bus.