performance: exclude lyrics if they are not enabled

internal/download/downloader.go

@@ -31,6 +31,9 @@ type Downloader struct {
 	barStarted   atomic.Int32
 }
 
+// downloadBufferSize sizes HTTP-to-disk copies. 1 MiB cuts read/write syscalls
+// ~32x vs Go's default 32 KiB io.Copy buffer, which matters for multi-MB FLAC
+// streams off CDNs that can sustain high per-connection throughput.
 const downloadBufferSize = 1 << 20
 
 func New() *Downloader {