fix: match scenario 2601 monthly seed progression

packages/logic/test/warUtils.test.ts

@@ -0,0 +1,15 @@
+import { describe, expect, it } from 'vitest';
+
+import { round } from '../src/war/utils.js';
+
+describe('legacy war rounding', () => {
+    it('matches PHP round() at drifted positive and negative half boundaries', () => {
+        expect(round(4159.499999999999)).toBe(4160);
+        expect(round(-4159.499999999999)).toBe(-4160);
+    });
+
+    it('keeps values meaningfully below a half boundary on the lower integer', () => {
+        expect(round(4159.499999)).toBe(4159);
+        expect(round(-4159.499999)).toBe(-4159);
+    });
+});