Solver Tracker Handles
Handle to every tracker attached to a single solver run.
Returned by SolverTrackingSpec.attachTo. The caller retains the handle for the lifetime of the run and invokes stopAll from a terminal-event handler (RunCompleted / RunFailed / RunCancelled) so the trackers release their file locks and detach their emitter connections.
Two internal lists are kept because the substrate's tracker base classes — ksl.simopt.solvers.trackers.AbstractSolverStateTracker and ksl.simopt.solvers.trackers.AbstractNestedSolverStateTracker — do not share a common ancestor. Both classes expose an independent stopTracking() method which stopAll invokes uniformly.