fix(planning): react only to calculations started by the mounted calendar

Re-mounting the calendar no longer records a duration sample or
announces the previous result, explanation or rejected explanation.
Starting a calculation during a cancellation announces loading and
keeps focus where it is. Only rejected explanation deliveries are
announced, as before. Replacement tests now replace a real plan.

Refs #275, #274

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

src/app/services/planning-calculation.service.ts

@@ -17,6 +17,7 @@ import { UserInputService } from './user-input-service';
 type Horizon = { start: string; end: string };
 
 interface PendingCalculation {
+	id: number;
 	horizon: Horizon;
 	progress: number;
 	cancelling: boolean;
@@ -78,6 +79,7 @@ export class PlanningCalculationService {
 	private readonly acceptedState = signal<AcceptedCalculation | null>(null);
 	private readonly explanationState = signal<PlanningExplanation | null>(null);
 	private readonly explanationErrorState = signal<PlanningReason | null>(null);
+	private readonly explanationRejectedState = signal(false);
 
 	readonly request = computed(() => {
 		const horizon = this.settings.planningHorizon();
@@ -101,6 +103,8 @@ export class PlanningCalculationService {
 	readonly accepted = this.acceptedState.asReadonly();
 	readonly explanation = this.explanationState.asReadonly();
 	readonly explanationError = this.explanationErrorState.asReadonly();
+	readonly explanationRejected = this.explanationRejectedState.asReadonly();
+	readonly pendingId = computed(() => this.pendingState()?.id ?? null);
 	readonly isCalculating = computed(() => this.pendingState() !== null);
 	readonly isCancelling = computed(() => this.pendingState()?.cancelling ?? false);
 	readonly progress = computed(() => this.pendingState()?.progress ?? 0);
@@ -124,7 +128,12 @@ export class PlanningCalculationService {
 		const requestedAt = performance.now();
 		const version = ++this.version;
 		this.userInput.declarationEntrySignal.set(false);
-		this.pendingState.set({ horizon: request.horizon, progress: 0, cancelling: false });
+		this.pendingState.set({
+			id: version,
+			horizon: request.horizon,
+			progress: 0,
+			cancelling: false,
+		});
 		let calculation: PlanningCalculationContext;
 		try {
 			calculation = this.calendar.createPlanningCalculation({
@@ -193,6 +202,7 @@ export class PlanningCalculationService {
 		const cancelling = this.pendingState()?.cancelling ?? false;
 		this.explanationState.set(null);
 		this.explanationErrorState.set(null);
+		this.explanationRejectedState.set(false);
 		this.pendingState.set(null);
 		this.acceptedState.set({
 			calculation,
@@ -209,7 +219,9 @@ export class PlanningCalculationService {
 	private loadArtifacts(calculation: PlanningCalculationContext): void {
 		const current = () => this.acceptedState()?.calculation === calculation;
 		const fail = (error: unknown) => {
-			if (current()) this.explanationErrorState.set(explanationFailure(error));
+			if (!current()) return;
+			this.explanationRejectedState.set(true);
+			this.explanationErrorState.set(explanationFailure(error));
 		};
 		calculation.explanation
 			.then((explanation) => current() && this.explanationState.set(explanation ?? null))