chore: update comments

Author: wjiayis

internal/services/toolkit/client/completion_v2.go

@@ -98,8 +98,9 @@ func (a *AIClientV2) ChatCompletionStreamV2(ctx context.Context, callbackStream
 			chunk := stream.Current()
 
 			if len(chunk.Choices) == 0 {
+				// Handle usage information
 				if chunk.Usage.TotalTokens > 0 {
-					// Record usage and log stats asynchronously to avoid blocking the response
+					// Record usage asynchronously to avoid blocking the response
 					go func(usage services.UsageRecord) {
 						bgCtx := context.Background()
 						if err := a.usageService.RecordUsage(bgCtx, usage); err != nil {

internal/services/usage.go

@@ -45,7 +45,7 @@ func NewUsageService(db *db.DB, cfg *cfg.Cfg, logger *logger.Logger) *UsageServi
 }
 
 // RecordUsage updates the active session or creates a new one if none exists.
-// Uses retry logic to handle race conditions when multiple requests try to create a session.
+// Falls back to update if insert fails (handles race when another request created a session). 
 func (s *UsageService) RecordUsage(ctx context.Context, record UsageRecord) error {
 	now := time.Now()
 	nowBson := bson.DateTime(now.UnixMilli())