fix(ui): resolve lint issues in file browser

pkg/ui/filebrowser.go

@@ -63,7 +63,7 @@ func MatchesExtension(name string, exts []string) bool {
 	}
 	ext := strings.ToLower(filepath.Ext(name))
 	for _, e := range exts {
-		if strings.ToLower(e) == ext {
+		if strings.EqualFold(e, ext) {
 			return true
 		}
 	}

pkg/ui/filebrowser_screens.go

@@ -87,8 +87,7 @@ func (se *SchemaEditor) showFileBrowser(cfg FileBrowserConfig) {
 		cfg.OnSelect(path)
 	}
 
-	var refresh func()
-	refresh = func() {
+	refresh := func() {
 		exts := cfg.Extensions
 		if !useFilter {
 			exts = nil