fix: surface reviewer response failures

frontend/src/shell/WidgetHost.tsx

@@ -1,3 +1,4 @@
+import { useRef, useState } from "react";
 import { useSessionStore } from "../store/sessionStore";
 import { resolve } from "../widgets";
 import { postResponse } from "../api/sessions";
@@ -9,9 +10,15 @@ export function WidgetHost({ sessionId }: { sessionId: string | null }) {
   const clearPending = useSessionStore((s) => s.clearPending);
   const pushToast = useSessionStore((s) => s.pushToast);
   const setLastUserEntry = useSessionStore((s) => s.setLastUserEntry);
+  const [responding, setResponding] = useState(false);
+  const responseInFlight = useRef(false);
   if (!pending) return null;
   const Renderer = resolve(pending.widget);
   const onRespond = async (r: UiResponse) => {
+    if (responseInFlight.current) return;
+    responseInFlight.current = true;
+    setResponding(true);
+
     if (sessionId) {
       try {
         await postResponse(sessionId, r);
@@ -24,9 +31,14 @@ export function WidgetHost({ sessionId }: { sessionId: string | null }) {
               ? `Failed to send response: ${err.message}`
               : "Failed to send response.",
         });
+        responseInFlight.current = false;
+        setResponding(false);
         return;
       }
     }
+    responseInFlight.current = false;
+    setResponding(false);
+    pushToast({ level: "success", text: "Response sent. The model is continuing." });
     setLastUserEntry({
       kind: "choice",
       text:
@@ -40,7 +52,16 @@ export function WidgetHost({ sessionId }: { sessionId: string | null }) {
   // widget render. resetKeys on the descriptor id so the next gate starts clean.
   return (
     <ErrorBoundary resetKeys={[pending.id]} label="step">
-      <Renderer descriptor={pending} onRespond={onRespond} sessionId={sessionId ?? undefined} />
+      <div className="space-y-2">
+        <fieldset disabled={responding} className="min-w-0 border-0 p-0">
+          <Renderer descriptor={pending} onRespond={onRespond} sessionId={sessionId ?? undefined} />
+        </fieldset>
+        {responding && (
+          <p role="status" aria-live="polite" className="text-sm text-muted-foreground">
+            Sending response…
+          </p>
+        )}
+      </div>
     </ErrorBoundary>
   );
 }