fix(396): mark active route in a default-collapsed group; fix mobile brand bar

Cold-review findings:
- #1 (CONFIRMED): deep-linking/reloading into a route inside a default-collapsed
  labeled group (e.g. /app/settings, /app/libraries) left the expanded sidebar
  with no active indicator, violating "active route marked in both states". Now
  the group that contains the active route is force-shown (and its header shows
  expanded) WITHOUT persisting — navigating away reverts to the stored preference.
  Regression test added.
- #2 (mobile): a persisted-collapsed state hid the brand logo+wordmark while the
  toggle is also hidden at <=980px, leaving an empty header. Restore the brand in
  the mobile query (collapse is desktop-only).

Verified live (Playwright): /app/settings deep-link shows Settings active +
aria-current, System auto-revealed, Media stays collapsed, nothing persisted.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

web/src/shell.css

@@ -3816,6 +3816,19 @@ body {
     display: none;
   }
 
+  /* The collapse feature is desktop-only (the nav is hidden here). If the sidebar was collapsed on
+     desktop, don't let the rail's brand-hiding leave an empty header on mobile — restore the brand
+     (#396). */
+  .ctv-app-shell-collapsed .ctv-brand {
+    padding: 0 14px;
+    justify-content: flex-start;
+  }
+
+  .ctv-app-shell-collapsed .ctv-brand img,
+  .ctv-app-shell-collapsed .ctv-brand-wordmark {
+    display: revert;
+  }
+
   .ctv-topbar {
     flex-wrap: wrap;
     height: auto;