fix(timers): unref background interval timers so they don't block clean shutdown (#4117)

Integrated into release/v3.8.28 (r8)

open-sse/services/autoRefreshDaemon.ts

@@ -79,6 +79,8 @@ class AutoRefreshDaemon {
     this.timerId = setInterval(() => {
       this.check().catch(() => {});
     }, this.checkIntervalMs);
+    // Don't keep the process alive solely for this periodic daemon.
+    (this.timerId as { unref?: () => void })?.unref?.();
 
     console.log(
       `[AutoRefreshDaemon] Started — checking ${this.credentialStore.size} credentials every ${this.checkIntervalMs / 1000}s`

src/lib/services/healthCheck.ts

@@ -25,6 +25,8 @@ export class HealthChecker {
     this.consecutiveFailures = 0;
     this.currentHealth = "unknown";
     this.timer = setInterval(() => void this.poll(), this.intervalMs);
+    // Don't keep the process alive solely for the health poller.
+    (this.timer as { unref?: () => void })?.unref?.();
   }
 
   stop(): void {

src/server/ws/liveServer.ts

@@ -440,6 +440,8 @@ function startHeartbeat(server: WebSocketServer): void {
       sendTo(client.ws, { type: "pong" } as WsServerMessage);
     }
   }, HEARTBEAT_INTERVAL_MS);
+  // Don't keep the process alive solely for the heartbeat (it is also cleared on close).
+  (interval as { unref?: () => void })?.unref?.();
 
   server.on("close", () => clearInterval(interval));
 }