The cloud library previously rendered its empty state while the first fetch
was still streaming ("No cloud strategies yet" during load), swallowed load
errors into empty lists, and swapped workspaces with no transition.

- Pulsing skeleton grid (folder pills + tiles) for the initial cloud fetch;
  folder navigation keeps previous data so it never flashes
- Error state with Retry (invalidates the library providers) instead of an
  empty grid masquerading as "no strategies"
- Cloud-unavailable state rebuilt on the shared message layout with a Log In
  action; community placeholder now uses the same shared layout
- 220ms cross-fade on workspace/section switches and on empty<->content
- Cloud empty states get icons; disabled rail items fade to 55% opacity

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