feat(dashboard): close legacy parity gaps

apps/dashboard/src/features/conversations/conversation-route.tsx

@@ -1,22 +1,38 @@
-import { useNavigate, useParams } from 'react-router-dom';
-import { ConversationsPage } from './conversations-page.js';
+import { useNavigate, useParams, useSearchParams } from 'react-router-dom';
+import { ConversationsPage, type ConversationFilters } from './conversations-page.js';
 
 export function ConversationRoute() {
   const navigate = useNavigate();
   const { conversationId } = useParams<{ conversationId: string }>();
+  const [searchParams, setSearchParams] = useSearchParams();
+  const filterValue = searchParams.get('filter');
+  const filters: ConversationFilters = {
+    search: searchParams.get('q') ?? '',
+    filter: filterValue === 'unread' || filterValue === 'awaiting-reply' ? filterValue : 'all',
+  };
 
   function selectConversation(nextConversationId: string | null) {
+    const suffix = searchParams.size > 0 ? `?${searchParams.toString()}` : '';
     void navigate(
       nextConversationId
-        ? `/conversations/${encodeURIComponent(nextConversationId)}`
-        : '/conversations',
+        ? `/conversations/${encodeURIComponent(nextConversationId)}${suffix}`
+        : `/conversations${suffix}`,
     );
   }
 
+  function updateFilters(next: ConversationFilters) {
+    const params = new URLSearchParams(searchParams);
+    if (next.search) params.set('q', next.search); else params.delete('q');
+    if (next.filter !== 'all') params.set('filter', next.filter); else params.delete('filter');
+    setSearchParams(params, { replace: true });
+  }
+
   return (
     <ConversationsPage
       selectedConversationId={conversationId ?? null}
       onSelectedConversationChange={selectConversation}
+      filters={filters}
+      onFiltersChange={updateFilters}
     />
   );
 }