fix(webui): keep new chat during session refresh

webui/src/hooks/useSessions.ts

@@ -27,13 +27,25 @@ export function useSessions(): {
   const [loading, setLoading] = useState(true);
   const [error, setError] = useState<string | null>(null);
   const tokenRef = useRef(token);
+  const optimisticKeysRef = useRef<Set<string>>(new Set());
   tokenRef.current = token;
 
   const refresh = useCallback(async () => {
     try {
       setLoading(true);
       const rows = await listSessions(tokenRef.current);
-      setSessions(rows);
+      const serverKeys = new Set(rows.map((row) => row.key));
+      setSessions((prev) => [
+        ...rows,
+        ...prev.filter(
+          (session) =>
+            optimisticKeysRef.current.has(session.key) &&
+            !serverKeys.has(session.key),
+        ),
+      ]);
+      for (const key of Array.from(optimisticKeysRef.current)) {
+        if (serverKeys.has(key)) optimisticKeysRef.current.delete(key);
+      }
       setError(null);
     } catch (e) {
       const msg =
@@ -57,6 +69,7 @@ export function useSessions(): {
   const createChat = useCallback(async (): Promise<string> => {
     const chatId = await client.newChat();
     const key = `websocket:${chatId}`;
+    optimisticKeysRef.current.add(key);
     // Optimistic insert; a subsequent refresh will replace it with the
     // authoritative row once the server persists the session.
     setSessions((prev) => [
@@ -77,6 +90,7 @@ export function useSessions(): {
   const deleteChat = useCallback(
     async (key: string) => {
       await apiDeleteSession(tokenRef.current, key);
+      optimisticKeysRef.current.delete(key);
       setSessions((prev) => prev.filter((s) => s.key !== key));
     },
     [],