fix: address code review findings

internal/scanner/scanner.go

@@ -6,6 +6,8 @@
 package scanner
 
 import (
+	"unicode/utf8"
+
 	"github.com/lithammer/fuzzysearch/fuzzy"
 	"naviwatcher/internal/normalize"
 )
@@ -44,10 +46,13 @@ func Similarity(a, b string) float64 {
 		return 0.0
 	}
 
+	// fuzzy.LevenshteinDistance operates on runes, so the comparison basis
+	// must be rune count, not byte length, to avoid biasing the score for
+	// non-ASCII titles (where bytes > runes).
 	dist := fuzzy.LevenshteinDistance(na, nb)
-	maxLen := len(na)
-	if len(nb) > maxLen {
-		maxLen = len(nb)
+	maxLen := utf8.RuneCountInString(na)
+	if rb := utf8.RuneCountInString(nb); rb > maxLen {
+		maxLen = rb
 	}
 
 	// 1.0 - normalized distance → higher is more similar.