strategyBacktestActivity
Emits the Strategy with refreshed runningBacktestCount when a backtest for this strategy crosses the boundary in or out of {running, pending}. Progress ticks (running → running) emit nothing; the server filters those server-side so the dashboard subscribes once and trusts every event.
Returns Strategy! (not a count delta) so Apollo's normalized cache merges the new count onto Strategy:<id> without any client-side cache surgery.
strategyBacktestActivity(
strategyID: ID!
): Strategy!