feat(ui): redesign voice cockpit with clinical companion drawer, Svelte 5 migration, and Gemini 3.8 voice

- Re-architect VoiceSession into full-bleed studio cockpit with overlay slide-over companion drawer
- Eliminate width squishing defect on LiveInsightPanel and add native dark/light theme support
- Integrate authentic Google Gemini 3.8 Flash TTS with Fenrir persona and fallback audio pipeline
- Implement comprehensive Playwright E2E visual regression suite across Desktop, iPad, and iPhone (21 tests, 45 snapshots)
- Migrate core application to Svelte 5 runes (, , ) with reactive stores
- Maintain .NET 8 Azure Functions serverless endpoints and clean build hygiene

test/audioEngine.test.ts

@@ -0,0 +1,161 @@
+import { describe, test, expect, vi, beforeEach, afterEach } from 'vitest';
+import { AudioEngine } from '../src/lib/audio/AudioEngine.svelte';
+import { UserSettingsStore } from '../src/lib/stores/UserSettingsStore.svelte';
+import type { Scenario } from '../types';
+
+describe('AudioEngine Reactive Controller', () => {
+  const mockScenario: Scenario = {
+    id: 'test-s1',
+    title: 'Silent Friend',
+    description: 'Friend has not replied to your text',
+    category: 'Relationships',
+    difficulty: 'Beginner',
+    systemInstruction: 'INTERNAL CBT LOGIC: You were just busy.',
+    initialMessage: 'Hey, sorry I was swamped yesterday.',
+    cbtFocus: ['Mind Reading'],
+    characterName: 'Sam'
+  };
+
+  let mockAudioContext: any;
+  let mockUserMediaStream: any;
+
+  beforeEach(() => {
+    mockAudioContext = {
+      state: 'running',
+      destination: {},
+      createAnalyser: () => ({
+        fftSize: 256,
+        frequencyBinCount: 128,
+        getByteFrequencyData: (arr: Uint8Array) => arr.fill(50)
+      }),
+      createMediaStreamSource: () => ({
+        connect: vi.fn()
+      }),
+      createBufferSource: () => ({
+        buffer: null,
+        connect: vi.fn(),
+        start: vi.fn(),
+        stop: vi.fn(),
+        onended: null
+      }),
+      decodeAudioData: async () => ({
+        duration: 2.0
+      }),
+      resume: vi.fn(),
+      close: vi.fn()
+    };
+
+    mockUserMediaStream = {
+      getTracks: () => [
+        {
+          stop: vi.fn()
+        }
+      ]
+    };
+
+    vi.stubGlobal('AudioContext', function () {
+      return mockAudioContext;
+    });
+
+    vi.stubGlobal('navigator', {
+      mediaDevices: {
+        getUserMedia: async () => mockUserMediaStream,
+        enumerateDevices: async () => []
+      }
+    });
+
+    vi.stubGlobal('requestAnimationFrame', (cb: FrameRequestCallback) => 1);
+    vi.stubGlobal('cancelAnimationFrame', vi.fn());
+  });
+
+  afterEach(() => {
+    vi.restoreAllMocks();
+  });
+
+  test('AudioEngine reports error if OpenRouter API key is missing', async () => {
+    const userSettings = new UserSettingsStore();
+    userSettings.openRouterApiKey = '';
+
+    const originalEnv = process.env.OPENROUTER_API_KEY;
+    try {
+      process.env.OPENROUTER_API_KEY = '';
+      const engine = new AudioEngine(mockScenario, userSettings);
+      await engine.start();
+
+      expect(engine.status).toBe('error');
+      expect(engine.errorMessage).toContain('OpenRouter API Key is missing');
+    } finally {
+      if (originalEnv !== undefined) process.env.OPENROUTER_API_KEY = originalEnv;
+    }
+  });
+
+  test('AudioEngine initializes, starts, and loads initial greeting when API key is present', async () => {
+    const userSettings = new UserSettingsStore();
+    userSettings.openRouterApiKey = 'sk-or-v1-mock-valid-key';
+
+    const engine = new AudioEngine(mockScenario, userSettings);
+    // Mock speakText to avoid real network call
+    engine.speakText = vi.fn();
+
+    await engine.start();
+
+    expect(engine.status).toBe('active');
+    expect(engine.errorMessage).toBe(null);
+    expect(engine.messages.length).toBe(1);
+    expect(engine.messages[0].text).toBe(mockScenario.initialMessage);
+    expect(engine.speakText).toHaveBeenCalledWith(mockScenario.initialMessage);
+
+    engine.destroy();
+  });
+
+  test('toggleMute toggles isMuted state and stops audio', async () => {
+    const userSettings = new UserSettingsStore();
+    const engine = new AudioEngine(mockScenario, userSettings);
+
+    expect(engine.isMuted).toBe(false);
+    engine.toggleMute();
+    expect(engine.isMuted).toBe(true);
+
+    engine.toggleMute();
+    expect(engine.isMuted).toBe(false);
+
+    engine.destroy();
+  });
+
+  test('stopAllAudio resets AI speaking flags and cancels speech synthesis', () => {
+    const cancelMock = vi.fn();
+    vi.stubGlobal('speechSynthesis', {
+      cancel: cancelMock,
+      speak: vi.fn()
+    });
+
+    const userSettings = new UserSettingsStore();
+    const engine = new AudioEngine(mockScenario, userSettings);
+    engine.isAiSpeaking = true;
+    engine.aiAudioLevel = 45;
+
+    engine.stopAllAudio();
+
+    expect(engine.isAiSpeaking).toBe(false);
+    expect(engine.aiAudioLevel).toBe(0);
+    expect(cancelMock).toHaveBeenCalled();
+
+    engine.destroy();
+  });
+
+  test('activeLevel derived property reflects active speaker volume', () => {
+    const userSettings = new UserSettingsStore();
+    const engine = new AudioEngine(mockScenario, userSettings);
+
+    engine.micLevel = 25;
+    engine.aiAudioLevel = 60;
+
+    engine.isAiSpeaking = false;
+    expect(engine.activeLevel).toBe(25);
+
+    engine.isAiSpeaking = true;
+    expect(engine.activeLevel).toBe(60);
+
+    engine.destroy();
+  });
+});