A signed-in person presses terminal and gets a shell over the agent tunnel. An API key cannot open one. The machine's own sshd is used when it is already listening; otherwise the agent starts a pty. The hub never installs or starts sshd.
Open an online Linux or FreeBSD machine. Terminal sits with discuss, control and watch. It opens a separate window, because a modal cannot hold the keyboard. On a phone the same button is in the bar above the navigation. The demo in this picture is painted online so the button is visible. It still has no tunnel, so pressing it here would say the machine is offline.
Copy and paste is text. Ctrl+C copies when something is selected, and otherwise interrupts the program. Ctrl+V pastes onto the machine. The text is not saved; the audit trail records that a transfer happened and how many bytes it was. The window itself is not part of this how-to.