fix: surface reviewer response failures

frontend/src/store/sessionStore.test.ts

@@ -235,6 +235,7 @@ test("an error-level info event flags the current phase", () => {
   expect(useSessionStore.getState().phaseError).toBe("F4");
   // the message still lands in stepMessages
   expect(useSessionStore.getState().stepMessages.at(-1)).toEqual({ level: "error", text: "boom" });
+  expect(useSessionStore.getState().toasts.at(-1)).toEqual({ level: "error", text: "boom" });
 });
 
 test("a non-error info event does not set phaseError", () => {

frontend/src/store/sessionStore.ts

@@ -167,7 +167,12 @@ export const useSessionStore = create<SessionState>((set) => ({
         ];
         // An error during the active phase marks that phase red until the next gate.
         return e.level === "error"
-          ? { stepMessages, activityLog, phaseError: st.currentPhase }
+          ? {
+              stepMessages,
+              activityLog,
+              phaseError: st.currentPhase,
+              toasts: [...st.toasts, { level: "error", text: e.text }],
+            }
           : { stepMessages, activityLog };
       }
       if (e.type === "system_event") {