chore(api): clarify cleaner comments and warning message

Address PR feedback: the inline comment in RunOnce contradicted what
evictExpired actually does, and the warning message referenced a
non-existent ErrNotFound precondition.

Author: jakubno

packages/api/internal/sandbox/storage/redis/cleaner.go

@@ -59,7 +59,8 @@ func (c *Cleaner) RunOnce(ctx context.Context) error {
 	var errs []error
 
 	// 1. globalExpirationSet: ExpiredItems internally ZREMs members whose sandbox JSON is gone (items.go:131-135).
-	// 2. Discard the returned sandbox list (only if older than StaleCutoff) since the cleaner is not responsible for removing sandboxes
+	// 2. evictExpired removes sandboxes whose EndTime is older than StaleCutoff;
+	//    recently expired ones are left to the evictor to avoid racing it.
 	expired, err := c.storage.ExpiredItems(ctx)
 	if err != nil {
 		errs = append(errs, fmt.Errorf("expiration index sweep: %w", err))
@@ -88,7 +89,7 @@ func (c *Cleaner) evictExpired(ctx context.Context, expired []sandbox.Sandbox) {
 		}
 
 		if rmErr := c.storage.Remove(context.WithoutCancel(ctx), sbx.TeamID, sbx.SandboxID); rmErr != nil {
-			logger.L().Warn(ctx, "Cleaner failed to purge stale Redis entry after ErrNotFound",
+			logger.L().Warn(ctx, "Cleaner failed to remove stale expired sandbox",
 				zap.Error(rmErr),
 				logger.WithSandboxID(sbx.SandboxID),
 				logger.WithTeamID(sbx.TeamID.String()),