List the human attention channels of the workspace bound to this credential. Telegram v0 allows at most ONE active destination per workspace. Pairing tokens and bot secrets are never returned. Each channel carries its own nudge window: timezone (IANA name, captured in the owner's browser at pairing, default UTC) plus push_window_start and push_window_end (local hours, end EXCLUSIVE, default 9 and 19). The hourly scheduled sweep only delivers to a channel when its local hour is inside that window; explicit pushes are never window-gated.