runStep

Advances algorithm state, then constructs and routes a snapshot only when a consumer actually needs it.

Consumer check — evaluated once per iteration:

val needsStep = saveSteps || stepEmitter.isObserved

When false: tight arithmetic loop with zero per-iteration heap allocation. When true:

• myCurrentStep is set (feeds Observable notification from IterativeProcess).

• If saveSteps: snapshot appended to _steps.

• If stepEmitter.isObserved and step matches snapShotFrequency: snapshot emitted.