security: strengthen session handling

surfaces/gui/src/App.tsx

@@ -695,6 +695,12 @@ export function App() {
             { kind: "notice", tone: "warn", text: "Error: " + (d.error || "unknown"), retriable: true },
           ]);
           break;
+        case "input_rejected":
+          setItems((p) => [
+            ...p,
+            { kind: "notice", tone: "warn", text: d.error || "That message was rejected." },
+          ]);
+          break;
         case "turn_done":
           setRunning(false);
           refreshSessions();

surfaces/gui/src/types.ts

@@ -15,6 +15,7 @@ export type EventType =
   | "iteration_end"
   | "turn_end"
   | "error"
+  | "input_rejected"
   | "interrupted"
   | "model_changed"
   | "turn_done";