The pitch runs on their data and dies before they leave

The prospect won't send sample data without an NDA, two legal reviews, and a month. So you stop asking them to send anything. In the pitch meeting, you spawn a container and close its firewall at the host kernel: nothing outbound, and nothing inside the box can change that. Their ops lead uploads the CSV. Your standard pipeline runs on it. On the conference room screen, a display URL with ?readonly=true shows the results building: they watch, they can't touch, nobody installed anything.

Then the close: you delete the container in front of them. Their data existed on a sealed machine for forty minutes, and now the machine doesn't exist.

Deleting the container is part of the pitch.