feat(desktop): add message more-actions dropdown menu

desktop/src/app/AppShell.tsx

@@ -561,6 +561,7 @@ export function AppShell() {
         <AppShellProvider
           value={{
             markChannelRead,
+            markChannelUnread,
             openChannelManagement: () => {
               setIsChannelManagementOpen(true);
             },

desktop/src/app/AppShellContext.tsx

@@ -5,11 +5,16 @@ type AppShellContextValue = {
     channelId: string,
     readAt: string | null | undefined,
   ) => void;
+  markChannelUnread: (
+    channelId: string,
+    lastMessageAt: string | null | undefined,
+  ) => void;
   openChannelManagement: () => void;
 };
 
 const AppShellContext = React.createContext<AppShellContextValue>({
   markChannelRead: () => {},
+  markChannelUnread: () => {},
   openChannelManagement: () => {},
 });
 

desktop/src/features/channels/ui/ChannelPane.tsx

@@ -82,6 +82,7 @@ type ChannelPaneProps = {
   onDelete?: (message: TimelineMessage) => void;
   onEdit?: (message: TimelineMessage) => void;
   onEditSave?: (content: string) => Promise<void>;
+  onMarkUnread?: (message: TimelineMessage) => void;
   onExpandThreadReplies: (message: TimelineMessage) => void;
   onJoinChannel?: () => Promise<void>;
   onOpenAgentSession: (pubkey: string) => void;
@@ -144,6 +145,7 @@ export const ChannelPane = React.memo(function ChannelPane({
   onDelete,
   onEdit,
   onEditSave,
+  onMarkUnread,
   onExpandThreadReplies,
   onJoinChannel,
   onOpenAgentSession,
@@ -339,6 +341,7 @@ export const ChannelPane = React.memo(function ChannelPane({
           messages={messages}
           onDelete={onDelete}
           onEdit={onEdit}
+          onMarkUnread={onMarkUnread}
           onReply={activeChannel?.archivedAt ? undefined : onOpenThread}
           onTargetReached={onTargetReached}
           onToggleReaction={onToggleReaction}
@@ -444,6 +447,7 @@ export const ChannelPane = React.memo(function ChannelPane({
           onDelete={onDelete}
           onEdit={onEdit}
           onEditSave={onEditSave}
+          onMarkUnread={onMarkUnread}
           onExpandReplies={onExpandThreadReplies}
           onSelectReplyTarget={onSelectThreadReplyTarget}
           onSend={onSendThreadReply}

desktop/src/features/channels/ui/ChannelScreen.tsx

@@ -33,6 +33,7 @@ import {
   formatTimelineMessages,
 } from "@/features/messages/lib/formatTimelineMessages";
 import { buildThreadPanelData } from "@/features/messages/lib/threadPanel";
+import type { TimelineMessage } from "@/features/messages/types";
 import { useFetchOlderMessages } from "@/features/messages/useFetchOlderMessages";
 import { useLoadMissingAncestors } from "@/features/messages/useLoadMissingAncestors";
 import { useChannelTyping } from "@/features/messages/useChannelTyping";
@@ -78,7 +79,8 @@ export function ChannelScreen({
   targetMessageEvent,
   targetMessageId,
 }: ChannelScreenProps) {
-  const { markChannelRead, openChannelManagement } = useAppShell();
+  const { markChannelRead, markChannelUnread, openChannelManagement } =
+    useAppShell();
   const [profilePanelPubkey, setProfilePanelPubkey] = React.useState<
     string | null
   >(null);
@@ -330,6 +332,16 @@ export function ChannelScreen({
         : undefined,
     [activeChannel, handleToggleReaction],
   );
+
+  const handleMarkUnread = React.useCallback(
+    (message: TimelineMessage) => {
+      if (!activeChannelId) return;
+      const messageIso = new Date(message.createdAt * 1_000).toISOString();
+      markChannelUnread(activeChannelId, messageIso);
+    },
+    [activeChannelId, markChannelUnread],
+  );
+
   const {
     channelAgentSessionAgents,
     closeAgentSession: handleCloseAgentSession,
@@ -477,6 +489,7 @@ export function ChannelScreen({
                   onEditSave={
                     activeChannel?.archivedAt ? undefined : handleEditSave
                   }
+                  onMarkUnread={handleMarkUnread}
                   onExpandThreadReplies={handleExpandThreadReplies}
                   onOpenAgentSession={handleOpenAgentSession}
                   onOpenDm={handleOpenDm}