perf(planning): reuse immutable non-working date counts

src/app/services/planning-objectives.ts

@@ -203,6 +203,9 @@ export interface OptimizationObservations {
 	leavePlacements: readonly { supporting: boolean }[];
 }
 
+// Calendar geometry reuses frozen date arrays across candidate plans.
+const nonWorkingDateCounts = new WeakMap<readonly string[], number>();
+
 export function evaluateOptimization(
 	configuration: OptimizationConfiguration,
 	observations: OptimizationObservations,
@@ -224,9 +227,14 @@ export function evaluateOptimization(
 				.map((week) => week.value);
 			break;
 		case 'time-off-periods':
-			values = observations.timeOffPeriods.map(
-				(period) => new Set(period.nonWorkingDates).size,
-			);
+			values = observations.timeOffPeriods.map(({ nonWorkingDates }) => {
+				const cached = nonWorkingDateCounts.get(nonWorkingDates);
+				if (cached !== undefined) return cached;
+				const count = new Set(nonWorkingDates).size;
+				if (Object.isFrozen(nonWorkingDates))
+					nonWorkingDateCounts.set(nonWorkingDates, count);
+				return count;
+			});
 			break;
 		case 'work-sequences':
 			values = observations.workSequences