merge: scenario 2400 long-run parity

packages/common/src/time/GameClock.ts

@@ -19,9 +19,9 @@ const requireSafeTick = (tick: number): number => {
 };
 
 const tickOffsetMilliseconds = (tick: number, ticksPerSecond: number): number => {
-    const wholeSeconds = Math.trunc(tick / ticksPerSecond);
+    const wholeSeconds = Math.floor(tick / ticksPerSecond);
     const remainingTicks = tick - wholeSeconds * ticksPerSecond;
-    const milliseconds = wholeSeconds * 1_000 + Math.round((remainingTicks * 1_000) / ticksPerSecond);
+    const milliseconds = wholeSeconds * 1_000 + Math.floor((remainingTicks * 1_000) / ticksPerSecond);
     if (!Number.isSafeInteger(milliseconds)) {
         throw new Error(`Game tick offset is outside the safe millisecond range: ${milliseconds}`);
     }
@@ -119,7 +119,7 @@ export class GameClock {
         const wholeSeconds = Math.trunc(milliseconds / 1_000);
         const remainingMilliseconds = milliseconds - wholeSeconds * 1_000;
         return requireSafeTick(
-            wholeSeconds * this.ticksPerSecond + Math.round((remainingMilliseconds * this.ticksPerSecond) / 1_000)
+            wholeSeconds * this.ticksPerSecond + Math.trunc((remainingMilliseconds * this.ticksPerSecond) / 1_000)
         );
     }
 }

packages/common/test/gameClock.test.ts

@@ -61,4 +61,17 @@ describe('GameClock', () => {
         expect(Number.isNaN(projected.getTime())).toBe(false);
         expect(clock.dateToTick(projected)).toBe(tick);
     });
+
+    it('truncates sub-millisecond projections like Ref GameClock', () => {
+        const clock = new GameClock({
+            baseTime,
+            tick: 0,
+            mode: 'manual',
+            wallAnchor: baseTime,
+            turnSeconds: 600,
+        });
+
+        expect(clock.tickToDate(14_115_919).toISOString()).toBe('2042-01-01T00:03:55.265Z');
+        expect(clock.tickToDate(-1).toISOString()).toBe('2041-12-31T23:59:59.999Z');
+    });
 });