feat(dashboard): Classic Split — 2-col layout, remove DashboardMentions widget

Restructures the dashboard to a lg:grid-cols-[1fr_300px] split:
- Left column: DashboardRecentDocuments (with stats footnote)
- Right column: DropZone (canWrite) + DashboardNeedsMetadata (flex-1)

Adds showRightColumn guard (canWrite || incompleteDocs.length > 0) so
read-only users with a complete archive never see an empty 300px ghost
column. DashboardMentions is removed from the page; the file is kept.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

frontend/src/routes/+page.svelte

@@ -6,7 +6,6 @@ import SearchFilterBar from './SearchFilterBar.svelte';
 import DropZone from './DropZone.svelte';
 import DocumentList from './DocumentList.svelte';
 import DashboardResumeStrip from '$lib/components/DashboardResumeStrip.svelte';
-import DashboardMentions from '$lib/components/DashboardMentions.svelte';
 import DashboardNeedsMetadata from '$lib/components/DashboardNeedsMetadata.svelte';
 import DashboardRecentDocuments from '$lib/components/DashboardRecentDocuments.svelte';
 import { m } from '$lib/paraglide/messages.js';
@@ -69,6 +68,11 @@ $effect(() => {
 	tagNames = data.filters?.tags || [];
 	if (hasAdvancedFilters(data.filters)) showAdvanced = true;
 });
+
+// Right column is only rendered when there is something to show.
+// Omitting it prevents an empty 300px ghost column for read-only users
+// with a complete archive.
+const showRightColumn = $derived(data.canWrite || (data.incompleteDocs?.length ?? 0) > 0);
 </script>
 
 <svelte:head>
@@ -94,20 +98,24 @@ $effect(() => {
 	{#if data.isDashboard}
 		<DashboardResumeStrip />
 
-		{#if data.canWrite}
-			<div class="mt-4">
-				<DropZone />
-			</div>
-		{/if}
+		<!-- Classic Split: left column (recent docs) + right column (upload + metadata queue) -->
+		<!-- No items-start — CSS Grid stretch default makes both columns equal height -->
+		<div class="mt-4 grid grid-cols-1 gap-4 {showRightColumn ? 'lg:grid-cols-[1fr_300px]' : ''}">
+			<DashboardRecentDocuments recentDocs={data.recentDocs ?? []} stats={data.stats} />
 
-		<div
-			class="mt-6 grid gap-4 {(data.mentions?.length ?? 0) > 0 && (data.incompleteDocs?.length ?? 0) > 0 ? 'lg:grid-cols-2' : ''}"
-		>
-			<DashboardMentions mentions={data.mentions ?? []} />
-			<DashboardNeedsMetadata incompleteDocs={data.incompleteDocs ?? []} />
-		</div>
-		<div class="mt-4">
-			<DashboardRecentDocuments recentDocs={data.recentDocs ?? []} />
+			{#if showRightColumn}
+				<div data-testid="dashboard-right-column" class="flex h-full flex-col gap-4">
+					{#if data.canWrite}
+						<DropZone />
+					{/if}
+					<!-- flex-1 + min-h-0 fills remaining height after DropZone.
+					     min-h-0 overrides the default min-height:auto that prevents flex
+					     children from shrinking below their content size. -->
+					<div class="flex min-h-0 flex-1 flex-col">
+						<DashboardNeedsMetadata incompleteDocs={data.incompleteDocs ?? []} />
+					</div>
+				</div>
+			{/if}
 		</div>
 	{:else}
 		<DocumentList documents={data.documents ?? []} canWrite={data.canWrite} error={data.error} />