fix: harden resume and SSE replay

frontend/src/store/sessionStore.test.ts

@@ -8,6 +8,29 @@ test("ui_request sets pendingWidget", () => {
   expect(useSessionStore.getState().pendingWidget?.id).toBe("u1");
 });
 
+test("the same gate descriptor id is handled once even after pending is cleared", () => {
+  const store = useSessionStore.getState();
+  const gate = {
+    type: "ui_request" as const,
+    ui_request: { id: "gate-1", widget: "select", title: "Review tables" },
+  };
+
+  store.applyEvent(gate);
+  store.applyEvent({
+    type: "ui_request",
+    ui_request: { ...gate.ui_request, title: "Duplicate transport copy" },
+  });
+  store.clearPending();
+  store.applyEvent(gate);
+
+  const state = useSessionStore.getState();
+  expect(state.pendingWidget).toBeNull();
+  expect(state.activityLog.filter((entry) => entry.kind === "gate")).toEqual([
+    { kind: "gate", phase: null, text: "Review tables" },
+  ]);
+  expect(state.seenGateIds).toEqual(new Set(["gate-1"]));
+});
+
 test("text_delta accumulates into transcript", () => {
   const s = useSessionStore.getState();
   s.applyEvent({ type: "text_delta", text: "Ana" });