避免误淘汰实时 DirectThread 订阅

仅在订阅游标落后于队列头时驱逐订阅，并补充队头被 pin 的回归测试。

apps/ai-game-creator-shell/src-tauri/src/agent/direct_thread_manager.rs

@@ -364,9 +364,15 @@ impl DirectThreadManager {
             let Some(thread) = self.threads.get_mut(thread_id) else {
                 return;
             };
+            let oldest_seq = thread
+                .events
+                .get(thread.head)
+                .map(|stored| stored.event.seq)
+                .unwrap_or(thread.next_seq.saturating_add(1));
             let slowest = thread
                 .subscribers
                 .iter()
+                .filter(|(_, subscriber)| subscriber.cursor < oldest_seq)
                 .min_by_key(|(_, subscriber)| subscriber.cursor)
                 .map(|(id, _)| id.clone());
             if let Some(subscription_id) = slowest {
@@ -530,6 +536,20 @@ mod tests {
         );
     }
 
+    #[test]
+    fn current_subscriber_is_not_expired_by_pinned_queue_head() {
+        let mut manager = DirectThreadManager::with_limits(2, 100_000);
+        manager.append("thread-1", draft("item.started", "turn-1", Some("item-1")));
+        let subscription = manager.subscribe("thread-1");
+        manager.append("thread-1", draft("item.delta", "turn-1", Some("item-1")));
+        manager.append("thread-1", draft("item.delta", "turn-1", Some("item-1")));
+        manager.append("thread-1", draft("item.delta", "turn-1", Some("item-1")));
+        assert_ne!(
+            manager.consume(&subscription.subscription_id),
+            Err(SUBSCRIPTION_EXPIRED.to_string())
+        );
+    }
+
     #[test]
     fn unresolved_approval_is_kept_in_bootstrap_until_resolved() {
         let mut manager = DirectThreadManager::with_limits(100, 100_000);