fix(frontend): track playback completion and meaningful inactivity

vocero-frontend/src/realtime/client.test.ts

@@ -9,6 +9,7 @@ const audio = vi.hoisted(() => ({
   close: vi.fn<() => Promise<void>>(),
   play: vi.fn(),
   clear: vi.fn(),
+  finishPlayback: vi.fn(),
   setMuted: vi.fn(),
   setGate: vi.fn(),
 }));
@@ -19,6 +20,7 @@ vi.mock("../audio/engine", () => ({
     close = audio.close;
     play = audio.play;
     clear = audio.clear;
+    finishPlayback = audio.finishPlayback;
     setMuted = audio.setMuted;
     setGate = audio.setGate;
   },
@@ -89,6 +91,33 @@ afterEach(() => {
 });
 
 describe("realtime session", () => {
+  it("waits for buffered audio to drain after response.done", async () => {
+    const client = new RealtimeClient(options());
+    const socket = await connect(client);
+    socket.receive({ type: "response.created", response: { id: "r1" } });
+    socket.receive({ type: "response.audio.delta", response_id: "r1", delta: "AAAA" });
+    socket.receive({ type: "response.done", response: { id: "r1", status: "completed" } });
+    await vi.waitFor(() => {
+      expect(audio.finishPlayback).toHaveBeenCalledOnce();
+    });
+    expect(client.status).toBe("ai-speaking");
+    audio.start.mock.calls[0]?.[3]();
+    expect(client.status).toBe("listening");
+    await client.close();
+  });
+  it("does not let a playback drain override a user interruption", async () => {
+    const client = new RealtimeClient(options());
+    const socket = await connect(client);
+    socket.receive({ type: "response.created", response: { id: "r1" } });
+    socket.receive({ type: "response.audio.delta", response_id: "r1", delta: "AAAA" });
+    socket.receive({ type: "input_audio_buffer.speech_started" });
+    await vi.waitFor(() => {
+      expect(client.status).toBe("user-speaking");
+    });
+    audio.start.mock.calls[0]?.[3]();
+    expect(client.status).toBe("user-speaking");
+    await client.close();
+  });
   it("starts microphone streaming without a session.updated acknowledgment", async () => {
     const client = new RealtimeClient(options());
     const pending = client.connect();