feat: add flags to ignore known non-music file extensions and update processor logic to support this feature

cmd/um/non_music_ext.go

@@ -0,0 +1,21 @@
+package main
+
+import (
+	"path/filepath"
+	"slices"
+	"strings"
+)
+
+// knownNonMusicExts are common non-audio suffixes to skip when walking dirs.
+var knownNonMusicExts = []string{
+	"",
+	".txt",
+	".mmkv",
+	".exe",
+	".dll",
+}
+
+func isKnownNonMusicExt(path string) bool {
+	ext := strings.ToLower(filepath.Ext(path))
+	return slices.Contains(knownNonMusicExts, ext)
+}