feat: performThink 10s休闲检查 + IsUserRecentlyActive — 后台让步前台

backend/ai-core/internal/background/thinker.go

@@ -408,6 +408,15 @@ func (t *Thinker) PushPlatformMessage(target ProactiveTarget, message string) {
 	}
 }
 
+
+
+// IsUserRecentlyActive returns true if the user has been active within the given duration.
+func (t *Thinker) IsUserRecentlyActive(d time.Duration) bool {
+	t.mu.Lock()
+	defer t.mu.Unlock()
+	return time.Since(t.lastUserMessage) < d
+}
+
 // ThinkerConfig 后台思考配置
 type ThinkerConfig struct {
 	Enabled          bool