SP0.9: sim-thread applier draining ActuatorCommandQueue via actuator ports

[Copilot]

Drains ActuatorCommandQueue (SP0.8) on the kDisco sim thread and applies each DispatchDecision through the SP0.6 actuator ports. All simulation mutation stays on the sim thread.

Mechanism choice: option 2 (generic ControlStepListener in :core)

Option 1 (standalone kDisco Process in :dispatcher-agent) is infeasible: Process.activate() must be called from the sim thread, but :core cannot import :dispatcher-agent types (circular dependency). A ControlStepListener interface in :core avoids the coupling — :dispatcher-agent implements it; :core only knows the interface.

:core changes

• ControlStepListener — new fun interface with single onControlStep(), placed in core/sim/. No dispatcher semantics, purely a sim-thread callback hook.
• ShuntingLoop — three additions:
  • var controlStepListener: ControlStepListener? — nullable field set by the wiring layer before context.run(); null by default so all existing callers are unaffected
  • fun approveQueuedTrain(trainId) — public delegate to the existing private applyApproveTrain, callable from the applier's callback
  • controlStepListener?.onControlStep() at the top of iteration(), before buildAdmissionObservation(), so drained decisions are visible to the inline dispatcher

:dispatcher-agent changes

• DispatchDecisionApplier — implements ControlStepListener; drains the queue and routes each decision:

class DispatchDecisionApplier(
    private val queue: ActuatorCommandQueue,
    private val networkPort: NetworkActuatorPort,
    private val onApproveTrain: (String) -> Unit,
) : ControlStepListener {
    override fun onControlStep() {
        queue.drain().forEach { applyDecision(it) }
    }
    private fun applyDecision(decision: DispatchDecision) = when (decision) {
        is DispatchDecision.ApproveTrain -> onApproveTrain(decision.trainId)
        is DispatchDecision.ReservePath  -> networkPort.requestRoute(decision.from, decision.to)
        is DispatchDecision.NoAction     -> Unit
    }
}

• DispatchDecisionApplierTest — 14 tests: decision routing per subtype, FIFO drain order, empty-queue no-ops, all RouteRequestResult outcomes, and four thread-identity assertions verifying that actuator calls and the approve callback execute on the onControlStep caller thread (never the posting/driver thread).

[sonarqubecloud]

Quality Gate failed

Failed conditions
25.0% Coverage on New Code (required ≥ 80%)

See analysis details on SonarQube Cloud