Verification showed FolderNavigatorSidebar is not mounted anywhere — the
visible "side rail" is _LibraryNavigationRail in folder_navigator.dart.
Apply the redesign goals to it: expanded width 226 -> 184, icons 21 -> 18,
rows 48 -> 40, and the per-item description line removed (moved to a
tooltip), so expanded items are a single clean label. Disabled cloud items
now fade to 55% opacity.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>