fix: serialize mock scenario event processing

Mock events were dispatched concurrently via setTimeout, causing
race conditions when modifying shared state. Added event queue to
ActiveStream that processes handlers sequentially while preserving
delay timing. Clear queue on cleanup to prevent orphaned events.

Author: ThomasK33

src/services/mock/mockScenarioPlayer.ts

@@ -112,6 +112,8 @@ interface MockPlayerDeps {
 interface ActiveStream {
   timers: NodeJS.Timeout[];
   messageId: string;
+  eventQueue: Array<() => Promise<void>>;
+  isProcessing: boolean;
 }
 
 export class MockScenarioPlayer {
@@ -216,16 +218,48 @@ export class MockScenarioPlayer {
     this.activeStreams.set(workspaceId, {
       timers,
       messageId: turn.assistant.messageId,
+      eventQueue: [],
+      isProcessing: false,
     });
 
     for (const event of turn.assistant.events) {
       const timer = setTimeout(() => {
-        void this.dispatchEvent(workspaceId, event, turn.assistant.messageId, historySequence);
+        this.enqueueEvent(workspaceId, () =>
+          this.dispatchEvent(workspaceId, event, turn.assistant.messageId, historySequence)
+        );
       }, event.delay);
       timers.push(timer);
     }
   }
 
+  private enqueueEvent(workspaceId: string, handler: () => Promise<void>): void {
+    const active = this.activeStreams.get(workspaceId);
+    if (!active) return;
+
+    active.eventQueue.push(handler);
+    void this.processQueue(workspaceId);
+  }
+
+  private async processQueue(workspaceId: string): Promise<void> {
+    const active = this.activeStreams.get(workspaceId);
+    if (!active || active.isProcessing) return;
+
+    active.isProcessing = true;
+
+    while (active.eventQueue.length > 0) {
+      const handler = active.eventQueue.shift();
+      if (!handler) break;
+
+      try {
+        await handler();
+      } catch (error) {
+        console.error(`[MockScenarioPlayer] Event handler error for ${workspaceId}:`, error);
+      }
+    }
+
+    active.isProcessing = false;
+  }
+
   private async dispatchEvent(
     workspaceId: string,
     event: MockAssistantEvent,
@@ -368,9 +402,15 @@ export class MockScenarioPlayer {
   private cleanup(workspaceId: string): void {
     const active = this.activeStreams.get(workspaceId);
     if (!active) return;
+
+    // Clear all pending timers
     for (const timer of active.timers) {
       clearTimeout(timer);
     }
+
+    // Clear event queue to prevent any pending events from processing
+    active.eventQueue = [];
+
     this.activeStreams.delete(workspaceId);
   }