Capture mock plus trusted-UI and device controls.
Erase a retained terminal capture as if expiresAt passed.
expiresAt
Device loss: fail with device-unavailable.
device-unavailable
Trusted Discard: cancel (reason: "user") or erase a terminal capture.
reason: "user"
Trusted Stop: complete with reason: "user".
Capture mock plus trusted-UI and device controls.