test(collections): compare the COLLECTIONS group with the concept

The concept hides COLLECTIONS at 950 px and below, which would leave a phone
no way to open a collection; production shows the rows there in the wrapped
layout of every other sidebar nav (D136). The shell comparison now compares
the group instead of filtering it out: the concept fixture seeds Landscapes
(12) and Experiments (8), the rows compare by name order, and at phone width
the nav compares against the concept's own sidebar-nav layout. The
collection rows are checked at 1600x1100 and 390x844 in both themes.

Part of #331

web/js/workspace/workspace.css

@@ -12,6 +12,9 @@ main:focus-visible { outline: 2px solid var(--ca-focus); outline-offset: 4px; }
    sidebar's min-content (the concept's `1fr`); the column is capped at the viewport as production's shell was. */
 @media (max-width: 950px) {
     .app-shell { grid-template-columns: minmax(0, 1fr); /* D31 */ }
+    /* D136 (#331): the concept hides COLLECTIONS here, which would leave a phone no way to open a collection; its rows
+       wrap like every other sidebar nav (the concept's `.sidebar nav` flex row). Its label stays hidden, as all are. */
+    #collections-nav { display: flex; /* D136 */ }
 }
 @media (forced-colors: active) {
     nav a[aria-current="page"] { border: 2px solid Highlight; color: LinkText; }