Make media browser file list feel native on macOS

Drop the iOS-grouped rounded card in MediaBrowserView's section
container for top/bottom dividers on macOS, force .buttonStyle(.plain)
on directory NavigationLinks to avoid default link tinting, and
shrink MediaFileRow's icon frame on macOS. iOS and tvOS unchanged.

Yattee/Views/MediaBrowser/MediaFileRow.swift

@@ -56,11 +56,19 @@ struct MediaFileRow: View {
     }
 
     private var iconView: some View {
+        #if os(macOS)
+        Image(systemName: file.systemImage)
+            .font(.title3)
+            .foregroundStyle(iconColor)
+            .frame(width: 28, height: 28)
+            .contentShape(Rectangle())
+        #else
         Image(systemName: file.systemImage)
             .font(.title2)
             .foregroundStyle(iconColor)
             .frame(width: 44, height: 44)
             .contentShape(Rectangle())
+        #endif
     }
 
     private var textView: some View {