fix(redis-worker): clear MollifierDrainer.stop() timeout timer when loop wins the race

The Promise.race between this.loopPromise and this.delay(timeoutMs)
discarded the timeout's underlying setTimeout handle whenever the loop
branch won. The discarded timer was still ref'd by libuv and pinned the
Node event loop alive for the remainder of `timeoutMs` — exactly the
shutdown slack the timeout was supposed to bound.

Inline the timer in stop() with a captured handle and clearTimeout() it
in a finally block, so every exit path (loop-won, timeout-won, throw)
releases the ref. The in-loop delay() calls are unchanged — they're
awaited normally and their timers fire-and-clear themselves.

Author: d-cs

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

@@ -130,16 +130,30 @@ export class MollifierDrainer<TPayload = unknown> {
       await this.loopPromise;
       return;
     }
+    // Hold the timer handle so we can clearTimeout() it after the race.
+    // Without this, when the loop wins the race, the discarded timer is
+    // still ref'd and pins the Node event loop for up to `timeoutMs`,
+    // delaying process shutdown by exactly the slack we were trying to
+    // bound. try/finally clears the handle in every exit path (loop-won,
+    // timeout-won, or exception).
     const timeoutSentinel = Symbol("mollifier.stop.timeout");
-    const winner = await Promise.race([
-      this.loopPromise.then(() => "done" as const),
-      this.delay(options.timeoutMs).then(() => timeoutSentinel),
-    ]);
-    if (winner === timeoutSentinel) {
-      this.logger.warn(
-        "MollifierDrainer.stop: deadline exceeded; returning while loop iteration is in flight",
-        { timeoutMs: options.timeoutMs },
-      );
+    let timeoutHandle: ReturnType<typeof setTimeout> | undefined;
+    const timeoutPromise = new Promise<typeof timeoutSentinel>((resolve) => {
+      timeoutHandle = setTimeout(() => resolve(timeoutSentinel), options.timeoutMs);
+    });
+    try {
+      const winner = await Promise.race([
+        this.loopPromise.then(() => "done" as const),
+        timeoutPromise,
+      ]);
+      if (winner === timeoutSentinel) {
+        this.logger.warn(
+          "MollifierDrainer.stop: deadline exceeded; returning while loop iteration is in flight",
+          { timeoutMs: options.timeoutMs },
+        );
+      }
+    } finally {
+      if (timeoutHandle) clearTimeout(timeoutHandle);
     }
   }