fix: use strings.HasPrefix instead of manual slice comparison

- Replace entry.Name()[:len(prefix)] == prefix with strings.HasPrefix
- Applied consistently in both deploy.go and export_test.go

internal/service/deploy/deploy.go

@@ -11,6 +11,7 @@ import (
 	"log/slog"
 	"os"
 	"path/filepath"
+	"strings"
 	"sync"
 	"time"
 
@@ -715,7 +716,7 @@ func (svc *Service) cleanupCancelledDeploy(
 	prefix := fmt.Sprintf("%d-", deployment.ID)
 
 	for _, entry := range entries {
-		if entry.IsDir() && len(entry.Name()) > len(prefix) && entry.Name()[:len(prefix)] == prefix {
+		if entry.IsDir() && strings.HasPrefix(entry.Name(), prefix) {
 			dirPath := filepath.Join(buildDir, entry.Name())
 
 			removeErr := os.RemoveAll(dirPath)

internal/service/deploy/export_test.go

@@ -6,6 +6,7 @@ import (
 	"log/slog"
 	"os"
 	"path/filepath"
+	"strings"
 
 	"git.eeqj.de/sneak/upaas/internal/config"
 	"git.eeqj.de/sneak/upaas/internal/docker"
@@ -47,7 +48,9 @@ func NewTestServiceWithConfig(log *slog.Logger, cfg *config.Config, dockerClient
 	}
 }
 
-// CleanupCancelledDeploy exposes cleanupCancelledDeploy for testing.
+// CleanupCancelledDeploy exposes the build directory cleanup portion of
+// cleanupCancelledDeploy for testing. It removes build directories matching
+// the deployment ID prefix.
 func (svc *Service) CleanupCancelledDeploy(
 	ctx context.Context,
 	appName string,
@@ -66,7 +69,7 @@ func (svc *Service) CleanupCancelledDeploy(
 	prefix := fmt.Sprintf("%d-", deploymentID)
 
 	for _, entry := range entries {
-		if entry.IsDir() && len(entry.Name()) > len(prefix) && entry.Name()[:len(prefix)] == prefix {
+		if entry.IsDir() && strings.HasPrefix(entry.Name(), prefix) {
 			dirPath := filepath.Join(buildDir, entry.Name())
 			_ = os.RemoveAll(dirPath)
 		}