Latest common-train stats, or undefined before first fetch.
Latest high-rate-donor stats, or undefined before first fetch.
true while the initial trains fetch is in flight.
Merged list of trains — query result folded with process-donations returns.
Refresh a single train's status (GET /get-updated-train-status/{trainID}).
Toggle a train's visibility (PATCH /trains/{trainID}).
Return shape for useDonationTrainState.