refactor: the server says a count one way, words.Count, for notifications, a wanted match's reason and the duplicate resolver's activity line (M505 #5643)

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

internal/library/duplicate_resolve.go

@@ -15,6 +15,7 @@ import (
 	"git.fabledsword.com/bvandeusen/minstrel/internal/db/dbq"
 	"git.fabledsword.com/bvandeusen/minstrel/internal/notifications"
 	syncpkg "git.fabledsword.com/bvandeusen/minstrel/internal/sync"
+	"git.fabledsword.com/bvandeusen/minstrel/internal/words"
 )
 
 // Duplicate resolver (M498 #5435, #5437; M502 #5517).
@@ -177,7 +178,7 @@ func ResolveDuplicates(
 	if res.Merged > 0 {
 		notifyAdmins(ctx, notifications.KindDuplicatesResolved, notifications.Payload{
 			Count:  int64(res.Merged),
-			Detail: fmt.Sprintf("Merged %d duplicate %s.", res.Merged, pluralWord(res.Merged, "copy", "copies")),
+			Detail: "Merged " + words.Count(res.Merged, "duplicate copy", "duplicate copies") + ".",
 		})
 	}
 	return res, nil
@@ -351,13 +352,6 @@ func autoMerge(
 	return nil
 }
 
-func pluralWord(n int, one, many string) string {
-	if n == 1 {
-		return one
-	}
-	return many
-}
-
 // DuplicateResolveWorker runs a resolver pass every hour.
 type DuplicateResolveWorker struct {
 	pool     *pgxpool.Pool