test(redis-worker): allow timer jitter in mollifier drainer stop-timeout test

Node's setTimeout can fire a millisecond or two early under CI load,
causing the existing `>= 500ms` lower bound to flake (saw 499ms in CI).
Loosen to `>= 450ms` — the behaviour being pinned is "stop honors the
deadline instead of waiting for the hung handler indefinitely", not
millisecond-precise timing.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

packages/redis-worker/src/mollifier/drainer.test.ts

@@ -1243,7 +1243,11 @@ describe("MollifierDrainer.start/stop", () => {
       await drainer.stop({ timeoutMs: 500 });
       const stopElapsed = Date.now() - stopStart;
 
-      expect(stopElapsed).toBeGreaterThanOrEqual(500);
+      // Allow a small jitter window below `timeoutMs` — Node's setTimeout can
+      // fire a millisecond or two early under CI load. The behaviour we're
+      // pinning is "stop honors the deadline instead of waiting for the hung
+      // handler indefinitely", not millisecond-precise timing.
+      expect(stopElapsed).toBeGreaterThanOrEqual(450);
       expect(stopElapsed).toBeLessThan(2_000);
     } finally {
       await buffer.close();