feat(sidebar-conversation-list): show empty-state hint inside expanded folders with no visible conversations

src/components/conversations/sidebar-conversation-list.tsx

@@ -335,6 +335,7 @@ interface FolderGroupItemProps {
   folderId: number
   folderName: string
   conversations: DbConversationSummary[]
+  totalConversationCount: number
   expanded: boolean
   importing: boolean
   reordering: boolean
@@ -367,6 +368,7 @@ function FolderGroupItem({
   folderId,
   folderName,
   conversations,
+  totalConversationCount,
   expanded,
   importing,
   reordering,
@@ -456,6 +458,18 @@ function FolderGroupItem({
           />
         </div>
         {expanded &&
+          (conversations.length === 0 ? (
+            <div
+              className="py-[0.375rem] text-[0.75rem] text-muted-foreground/70"
+              style={{
+                paddingLeft: "calc(var(--conv-rail-axis) + 0.875rem)",
+              }}
+            >
+              {totalConversationCount === 0
+                ? t("emptyFolderHint")
+                : t("noMatchingConversations")}
+            </div>
+          ) : (
             conversations.map((conv) => (
               <SidebarConversationCard
                 key={`conv-${conv.agent_type}-${conv.id}`}
@@ -477,6 +491,7 @@ function FolderGroupItem({
                 onStatusChange={onStatusChange}
                 onNewConversation={onNewConversation}
               />
+            ))
           ))}
       </Reorder.Item>
     </div>
@@ -619,6 +634,14 @@ export function SidebarConversationList({
     return map
   }, [filteredConversations, sortMode])
 
+  const folderTotalCounts = useMemo(() => {
+    const map = new Map<number, number>()
+    for (const conv of conversations) {
+      map.set(conv.folder_id, (map.get(conv.folder_id) ?? 0) + 1)
+    }
+    return map
+  }, [conversations])
+
   const orderedFolderIds = useMemo(() => {
     const folderIdSet = new Set(folders.map((f) => f.id))
     // During drag we honour the optimistic order so sibling folders shift live
@@ -1036,6 +1059,9 @@ export function SidebarConversationList({
                         folderId={folderId}
                         folderName={folderName}
                         conversations={convsWithKey}
+                        totalConversationCount={
+                          folderTotalCounts.get(folderId) ?? 0
+                        }
                         expanded={expanded}
                         importing={importing}
                         reordering={reordering}