fix(heartbeat): improve lock heartbeat shutdown handling

changelog.md

@@ -3,6 +3,12 @@
 ## Pending
 
 
+### Fixes
+
+- improve lock heartbeat shutdown handling (heartbeat)
+  - Replaces the stop signal promise race with an explicit wake callback for the heartbeat wait loop
+  - Ensures the heartbeat loop can be interrupted cleanly when stopping without leaving the timer pending
+
 ## 2026-05-19 - 1.4.0
 
 ### Features

ts/classes.smartmigration.ts

@@ -544,16 +544,22 @@ export class SmartMigration {
   private startLockHeartbeat(ledger: Ledger): ILockHeartbeat {
     const intervalMs = this.getLockHeartbeatMs();
     let stopped = false;
-    let resolveStop!: () => void;
+    let wakeWaiter: (() => void) | null = null;
     let lockError: SmartMigrationError | null = null;
 
-    const stopSignal = new Promise<void>((resolve) => {
-      resolveStop = resolve;
-    });
-
     const loopPromise = (async () => {
       while (!stopped) {
-        await Promise.race([this.sleep(intervalMs), stopSignal]);
+        await new Promise<void>((resolve) => {
+          const timeout = setTimeout(() => {
+            wakeWaiter = null;
+            resolve();
+          }, intervalMs);
+          wakeWaiter = () => {
+            clearTimeout(timeout);
+            wakeWaiter = null;
+            resolve();
+          };
+        });
         if (stopped) {
           return;
         }
@@ -589,7 +595,7 @@ export class SmartMigration {
         }
 
         stopped = true;
-        resolveStop();
+        wakeWaiter?.();
         await loopPromise;
       },
     };