Returns the caller's open (running or paused) stopwatch session, or `data: null`. Elapsed time is derived from `segments`; `active_ms` and `server_now` are computed by the server. `user_id` reads another user's session and requires delegation rights (time_sheet:approve plus read_all or manager-of-subject).
Success response 200 · schema WorkV1StopwatchActiveResponse
runningpausedloggeddiscarded