Add cabpack generation with default mode and file organization

pkg/wav/reader.go

@@ -36,6 +36,15 @@ func toMono(data []float64, channels int) []float64 {
 
 // ReadWAVFile reads a WAV file and returns its PCM data as float64 (resampled to 96kHz mono)
 func ReadWAVFile(filePath string) (*WAVData, error) {
+	// Check if path is a directory
+	info, err := os.Stat(filePath)
+	if err != nil {
+		return nil, fmt.Errorf("failed to access file %s: %w", filePath, err)
+	}
+	if info.IsDir() {
+		return nil, fmt.Errorf("path %s is a directory, not a WAV file", filePath)
+	}
+
 	file, err := os.Open(filePath)
 	if err != nil {
 		return nil, fmt.Errorf("failed to open file %s: %w", filePath, err)