feat: preserve legacy nation turn execution

app/game-engine/src/turn/nationTurnMonthlyHandler.ts

@@ -0,0 +1,38 @@
+import { asRecord } from '@sammo-ts/common';
+
+import type { InMemoryTurnWorld, TurnCalendarHandler } from './inMemoryWorld.js';
+
+const decrementLimit = (value: unknown): number => {
+    if (typeof value === 'number' && Number.isFinite(value)) {
+        return Math.max(0, Math.floor(value) - 1);
+    }
+    if (typeof value === 'string') {
+        const parsed = Number(value);
+        if (Number.isFinite(parsed)) {
+            return Math.max(0, Math.floor(parsed) - 1);
+        }
+    }
+    return 0;
+};
+
+// ref preUpdateMonthly(): 전략 제한과 외교 제한은 매 월턴마다 1씩 감소한다.
+export const createNationTurnMonthlyHandler = (options: {
+    getWorld: () => InMemoryTurnWorld | null;
+}): TurnCalendarHandler => ({
+    onMonthChanged: () => {
+        const world = options.getWorld();
+        if (!world) {
+            return;
+        }
+        for (const nation of world.listNations()) {
+            const meta = asRecord(nation.meta);
+            world.updateNation(nation.id, {
+                meta: {
+                    ...nation.meta,
+                    strategic_cmd_limit: decrementLimit(meta.strategic_cmd_limit),
+                    surlimit: decrementLimit(meta.surlimit),
+                },
+            });
+        }
+    },
+});