fix: address code review findings (consolidate slice helpers, correct bootleg comment)

internal/config/config.go

@@ -48,10 +48,13 @@ type TelegramConfig struct {
 
 // ScannerConfig holds scanner engine parameters.
 //
-// Bootleg/Compilation filtering is intentionally unconditional: bootlegs,
-// promotions, and pseudo-releases are always excluded (musicbrainz/api.go),
-// and compilations are always included. These are not user-toggleable, so
-// there are no corresponding config fields.
+// Type filtering is handled in musicbrainz/api.go, not here: only Album/Single/EP
+// primary types (and release groups whose secondary types include Single/EP/Compilation)
+// are included. Bootlegs are not explicitly excluded — a release group whose primary
+// type is an included type but whose secondary types include "Bootleg" will still pass
+// through and may be reported as missing. Compilations are included by default but can
+// be excluded per-artist via artist_settings.ignore_compilations. These behaviours are
+// not user-toggleable at the global config level, so there are no corresponding config fields.
 type ScannerConfig struct {
 	FuzzyThreshold float64 `yaml:"fuzzy_threshold"`
 }