refactor(usage): replace channel-based queue with mutex-protected slice

- Switched to a slice-based queue with mutex and condition variable for better control over queuing and dispatching.
- Removed fixed buffer size to handle dynamic queuing.
- Enhanced shutdown logic to safely close the queue and wake up waiting goroutines.

sdk/cliproxy/usage/manager.go

@@ -42,7 +42,11 @@ type Manager struct {
 	once     sync.Once
 	stopOnce sync.Once
 	cancel   context.CancelFunc
-	queue    chan queueItem
+
+	mu     sync.Mutex
+	cond   *sync.Cond
+	queue  []queueItem
+	closed bool
 
 	pluginsMu sync.RWMutex
 	plugins   []Plugin
@@ -50,10 +54,9 @@ type Manager struct {
 
 // NewManager constructs a manager with a buffered queue.
 func NewManager(buffer int) *Manager {
-	if buffer <= 0 {
-		buffer = 256
-	}
-	return &Manager{queue: make(chan queueItem, buffer)}
+	m := &Manager{}
+	m.cond = sync.NewCond(&m.mu)
+	return m
 }
 
 // Start launches the background dispatcher. Calling Start multiple times is safe.
@@ -80,7 +83,10 @@ func (m *Manager) Stop() {
 		if m.cancel != nil {
 			m.cancel()
 		}
-		close(m.queue)
+		m.mu.Lock()
+		m.closed = true
+		m.mu.Unlock()
+		m.cond.Broadcast()
 	})
 }
 
@@ -102,40 +108,30 @@ func (m *Manager) Publish(ctx context.Context, record Record) {
 	}
 	// ensure worker is running even if Start was not called explicitly
 	m.Start(context.Background())
-	select {
-	case m.queue <- queueItem{ctx: ctx, record: record}:
-	default:
-		// queue is full; drop the record to avoid blocking runtime paths
-		log.Debugf("usage: queue full, dropping record for provider %s", record.Provider)
+	m.mu.Lock()
+	if m.closed {
+		m.mu.Unlock()
+		return
 	}
+	m.queue = append(m.queue, queueItem{ctx: ctx, record: record})
+	m.mu.Unlock()
+	m.cond.Signal()
 }
 
 func (m *Manager) run(ctx context.Context) {
 	for {
-		select {
-		case <-ctx.Done():
-			m.drain()
-			return
-		case item, ok := <-m.queue:
-			if !ok {
-				return
-			}
-			m.dispatch(item)
+		m.mu.Lock()
+		for !m.closed && len(m.queue) == 0 {
+			m.cond.Wait()
 		}
-	}
-}
-
-func (m *Manager) drain() {
-	for {
-		select {
-		case item, ok := <-m.queue:
-			if !ok {
-				return
-			}
-			m.dispatch(item)
-		default:
+		if len(m.queue) == 0 && m.closed {
+			m.mu.Unlock()
 			return
 		}
+		item := m.queue[0]
+		m.queue = m.queue[1:]
+		m.mu.Unlock()
+		m.dispatch(item)
 	}
 }