fix frontend invoke result handling

frontend/src/a2a.js

@@ -1,5 +1,11 @@
 export const CONFIG_URL = import.meta.env.DEV ? "/config.json" : "./config.json";
 
+export function unwrapInvokeResponse(payload) {
+  return payload && typeof payload === "object" && "result" in payload
+    ? payload.result
+    : payload;
+}
+
 export async function requestJson(url, init = {}) {
   const response = await fetch(url, { credentials: "same-origin", ...init });
   const text = await response.text();
@@ -19,14 +25,20 @@ export async function loadSession(config) {
   return requestJson(config.endpoints.session);
 }
 
+export function signInUrl(config) {
+  const target = config.auth?.authorizeUrl || config.auth?.loginUrl;
+  if (!target) return null;
+  const next = encodeURIComponent(
+    window.location.pathname + window.location.search + window.location.hash,
+  );
+  return `${target}${target.includes("?") ? "&" : "?"}next=${next}`;
+}
+
 export async function requireSession(config) {
   const session = await loadSession(config);
   if (!session?.authenticated) {
-    const loginUrl = config.auth?.loginUrl;
-    if (loginUrl) {
-      const next = encodeURIComponent(window.location.href);
-      window.location.assign(`${loginUrl}${loginUrl.includes("?") ? "&" : "?"}next=${next}`);
-    }
+    const target = signInUrl(config);
+    if (target) window.location.assign(target);
     throw new Error("sign in required");
   }
   return session;
@@ -36,7 +48,7 @@ export async function callSkill(config, skillName, args) {
   if (config.auth?.invokeRequiresSession) {
     await requireSession(config);
   }
-  return requestJson(
+  const payload = await requestJson(
     `${config.endpoints.invoke}/${encodeURIComponent(skillName)}`,
     {
       method: "POST",
@@ -44,6 +56,7 @@ export async function callSkill(config, skillName, args) {
       body: JSON.stringify({ arguments: args }),
     },
   );
+  return unwrapInvokeResponse(payload);
 }
 
 export function sampleValue(schema) {