feat: add unread message indicators on sidebar sessions

Show a cyan dot on sessions that received new messages while
viewing a different session. The dot clears when switching to
that session.

src/components/Sidebar.tsx

@@ -147,6 +147,9 @@ export function Sidebar({ sessions, activeSession, onSwitch, open, onClose }: Pr
                   {s.isActive && (
                     <span className="absolute -top-0.5 -right-0.5 h-2 w-2 rounded-full bg-violet-400 shadow-[0_0_8px_rgba(168,85,247,0.7)] animate-pulse" />
                   )}
+                  {s.hasUnread && !isActive && (
+                    <span className="absolute -top-0.5 -left-0.5 h-2 w-2 rounded-full bg-cyan-400 shadow-[0_0_8px_rgba(34,211,238,0.7)]" />
+                  )}
                 </div>
                 <div className="flex-1 min-w-0">
                   <div className="flex items-center gap-1">

src/hooks/useGateway.ts

@@ -41,6 +41,7 @@ export function useGateway() {
   useEffect(() => { activeSessionRef.current = activeSession; }, [activeSession]);
   const currentRunIdRef = useRef<string | null>(null);
   const [activeSessions, setActiveSessions] = useState<Set<string>>(new Set());
+  const [unreadSessions, setUnreadSessions] = useState<Set<string>>(new Set());
 
   const handleAgentEvent = useCallback((payload: JsonPayload) => {
     if (payload?.stream !== 'tool') return;
@@ -241,7 +242,18 @@ export function useGateway() {
         }
       }
 
-      if (evtSession !== activeSessionRef.current) return;
+      if (evtSession !== activeSessionRef.current) {
+        // Mark non-active sessions as unread when they receive a final message
+        if (state === 'final' && evtSession) {
+          setUnreadSessions(prev => {
+            if (prev.has(evtSession)) return prev;
+            const next = new Set(prev);
+            next.add(evtSession);
+            return next;
+          });
+        }
+        return;
+      }
 
       if (state === 'delta') {
         const text = extractText(message);
@@ -358,6 +370,12 @@ export function useGateway() {
     setActiveSession(key);
     activeSessionRef.current = key;
     setMessages([]);
+    setUnreadSessions(prev => {
+      if (!prev.has(key)) return prev;
+      const next = new Set(prev);
+      next.delete(key);
+      return next;
+    });
     loadHistory(key);
   }, [loadHistory]);
 
@@ -388,6 +406,7 @@ export function useGateway() {
   const enrichedSessions = sessions.map(s => ({
     ...s,
     isActive: activeSessions.has(s.key),
+    hasUnread: unreadSessions.has(s.key),
   }));
 
   return {

src/types/index.ts

@@ -20,6 +20,7 @@ export interface Session {
   label?: string;
   messageCount?: number;
   isActive?: boolean;
+  hasUnread?: boolean;
   totalTokens?: number;
   contextTokens?: number;
   inputTokens?: number;