frontend: one grid for every lens, and a cross-fade between surfaces (task 1913)

"The same board, re-filtered" has to be literally true to read as true. The
column classes were copy-pasted into five places — the board's pinned and other
sections, its non-board branch, search, and timeline — so a lens could drift from
home by a single edit. One already had: the FLIP reflow from 1914 landed on the
board's three grids and left search and timeline popping. NoteGrid is now the only
file that knows how the masonry is laid out or how it moves, and search and
timeline gained the motion by adopting it.

It takes activeId rather than an index. The board splits its notes across two
grids, so index-based focus made the call site do offset arithmetic
(focusedIndex === pinnedNotes.length + i) against a list the grid didn't own.

The lens cross-fade is deliberately UNKEYED, which is the whole trick. Board,
archive, trash and label all render the same BoardView; keying the transition on
the route would remount it, blanking the board and refetching — exactly the
page-change feeling this is meant to remove. Unkeyed, Vue transitions only when
the component TYPE changes (board to search to timeline to graph), and moving
between the board's own lenses stays an in-place reflow that NoteGrid animates.
The two behaviours fall out of one rule rather than needing to be special-cased.

Out is quicker than in because mode="out-in" makes the durations additive.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

frontend/src/views/SearchView.vue

@@ -6,7 +6,7 @@ import { useNoteList } from "../composables/useNoteList";
 import { useNoteEditor } from "../composables/useNoteEditor";
 import AsyncState from "../components/AsyncState.vue";
 import EmptyState from "../components/EmptyState.vue";
-import NoteCard from "../components/NoteCard.vue";
+import NoteGrid from "../components/NoteGrid.vue";
 import NoteEditor from "../components/NoteEditor.vue";
 
 const route = useRoute();
@@ -38,9 +38,7 @@ watch(query, run, { immediate: true });
 
     <AsyncState :loading="loading" :error="error || undefined" error-title="Couldn't search" @retry="run">
       <EmptyState v-if="query && results.length === 0" title="No matches" :subtitle="noMatchSubtitle" />
-      <div v-else-if="results.length" class="columns-1 gap-4 sm:columns-2 lg:columns-3 xl:columns-4">
-        <NoteCard v-for="n in results" :key="n.id" :note="n" @open="openEditor" />
-      </div>
+      <NoteGrid v-else-if="results.length" :notes="results" @open="openEditor" />
     </AsyncState>
   </div>