feat(call): add streaming voice call experience

src/app/call/__tests__/voice-call-player.test.ts

@@ -0,0 +1,57 @@
+import { afterEach, describe, expect, it, vi } from "vitest";
+
+import { VoiceCallPlayer } from "@/app/call/voice-call-player";
+
+describe("VoiceCallPlayer", () => {
+  afterEach(() => {
+    vi.unstubAllGlobals();
+  });
+
+  it("schedules decoded sentence audio on one continuous Web Audio timeline", async () => {
+    const starts: number[] = [];
+    const sources: Array<{ onended: (() => void) | null }> = [];
+    const context = {
+      state: "running",
+      currentTime: 0,
+      destination: {},
+      resume: vi.fn(async () => undefined),
+      close: vi.fn(async () => undefined),
+      decodeAudioData: vi.fn(async () => ({ duration: 1 })),
+      createBufferSource: vi.fn(() => {
+        const source = {
+          buffer: null,
+          onended: null as (() => void) | null,
+          connect: vi.fn(),
+          disconnect: vi.fn(),
+          stop: vi.fn(),
+          start: vi.fn((at: number) => starts.push(at)),
+        };
+        sources.push(source);
+        return source;
+      }),
+    };
+    vi.stubGlobal("AudioContext", function AudioContextMock() {
+      return context;
+    });
+
+    const player = new VoiceCallPlayer();
+    const gaps: number[] = [];
+    player.onGap = (milliseconds) => gaps.push(milliseconds);
+    const meta = {
+      callId: "call-1",
+      turnId: "turn-1",
+      index: 0,
+      mimeType: "audio/mpeg",
+      byteLength: 3,
+    };
+
+    player.enqueue(meta, new Uint8Array([1, 2, 3]).buffer);
+    player.enqueue({ ...meta, index: 1 }, new Uint8Array([4, 5, 6]).buffer);
+
+    await vi.waitFor(() => expect(starts).toHaveLength(2));
+    expect(starts).toEqual([0.025, 1.025]);
+    expect(gaps).toEqual([0]);
+    expect(sources).toHaveLength(2);
+    player.dispose();
+  });
+});