feat(maestro): concatenate queued structured prompts into one turn

Closes #257

web/src/components/structured/StructuredPane.test.tsx

@@ -323,6 +323,26 @@ describe("prompt and cancel", () => {
     await waitFor(() => expect(sendStructuredPrompt).toHaveBeenCalledWith("s1", "next up"));
   });
 
+  it("concatenates multiple queued messages into a single prompt", async () => {
+    const { socket } = mount();
+    snapshot(socket, [], busy);
+    const input = document.querySelector<HTMLTextAreaElement>(".structured-input")!;
+    const form = document.querySelector("form.structured-composer")!;
+
+    fireEvent.change(input, { target: { value: "first" } });
+    fireEvent.submit(form);
+    fireEvent.change(input, { target: { value: "second" } });
+    fireEvent.submit(form);
+
+    expect(sendStructuredPrompt).not.toHaveBeenCalled();
+    const queued = document.querySelectorAll(".st-row-queued");
+    expect(queued).toHaveLength(2);
+
+    socket.emit({ type: "reduced_state", state: idle });
+    await waitFor(() => expect(sendStructuredPrompt).toHaveBeenCalledWith("s1", "first\n\nsecond"));
+    expect(sendStructuredPrompt).toHaveBeenCalledTimes(1);
+  });
+
   it("hands a failed send's draft back to the operator", async () => {
     vi.mocked(sendStructuredPrompt).mockRejectedValueOnce(new Error("boom"));
     const { socket } = mount();

web/src/components/structured/StructuredPane.tsx

@@ -251,14 +251,16 @@ export const StructuredPane = forwardRef<StructuredPaneHandle, StructuredPanePro
     [sessionId, socketGeneration, session],
   );
 
-  // A queued message goes out as soon as the projected turn is idle — the
-  // daemon answers a second prompt `409 turn_in_flight`, so the queue is
-  // client-local (docs/STRUCTURED-VIEW.md).
+  // Queued messages are concatenated into a single prompt so the agent sees
+  // one user turn instead of N back-to-back turns. The daemon rejects a
+  // second prompt while a turn is in flight (`409 turn_in_flight`), so the
+  // queue is client-local (docs/STRUCTURED-VIEW.md).
   useEffect(() => {
     if (active || promptPending.current || queue.length === 0) return;
-    const [next, ...rest] = queue;
-    setQueue(rest);
-    dispatchPrompt(next.text, next.attachments);
+    const text = queue.map((q) => q.text).join("\n\n");
+    const files = queue.flatMap((q) => q.attachments);
+    setQueue([]);
+    dispatchPrompt(text, files);
   }, [active, queue, dispatchPrompt]);
 
   const submit = (text: string, files: File[]) => {