Make "end session" a desktop icon

[putty182]

Just curious, instead of using cloud functions to cleanup upon shutdown, how about using gcloud alpha cloud-shell + nohup as an alternative to run the cleanup script(snapshots and so on).

Originally posted by @juzkev in #4 (comment)

Implement a desktop shortcut, within the rig, that triggers scale-down.sh activities. One option is to trigger a nohup'd command via gcloud alpha cloud-shell to trigger the scale down (being careful to appease cloud-shell's keep-alive checks)

Bonus points:
make this run only when a human "clicks shutdown" in windows (e.g. explictly only windows-initiated shutdowns, not GCP initiated ones which will occur via ACPI G2 Soft Off)

Doesn't seem to be a way to reliably react only to ACPI G2 via Windows, so perhaps there might be something in GCP that could trigger this.