fix(test): allow timing variance in StaleExpirationMap remaining TTL test

setTimeout isn't exact, so the remaining TTL after 100ms wait may be
slightly more than expected (901ms instead of ≤900ms). Adding 10ms
tolerance to prevent flaky test failures.

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

test/utils/stale-expiration-map.test.ts

@@ -228,7 +228,8 @@ describe('StaleExpirationMap', () => {
 
       const remaining = map.getRemainingTtl('a');
       expect(remaining).toBeDefined();
-      expect(remaining!).toBeLessThanOrEqual(900);
+      // Allow small timing variance (setTimeout isn't exact)
+      expect(remaining!).toBeLessThanOrEqual(910);
       expect(remaining!).toBeGreaterThan(800);
 
       map.dispose();