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/audioUtils.test.ts

@@ -0,0 +1,99 @@
+import { describe, test, expect } from 'vitest';
+import {
+  floatTo16BitPCM,
+  encodeBase64,
+  decodeBase64,
+  decodeAudioData
+} from '../services/audioUtils';
+
+describe('Audio Utilities & PCM DSP', () => {
+  test('floatTo16BitPCM converts Float32Array to 16-bit PCM buffer with proper clamping', () => {
+    // Input with values within range, positive clamp (>1), negative clamp (<-1), and zero
+    const input = new Float32Array([0.0, 0.5, 1.0, 1.5, -0.5, -1.0, -1.5]);
+    const buffer = floatTo16BitPCM(input);
+
+    expect(buffer.byteLength).toBe(input.length * 2);
+
+    const view = new DataView(buffer);
+    // 0.0 -> 0
+    expect(view.getInt16(0, true)).toBe(0);
+    // 0.5 -> 0.5 * 32767 = 16383.5 -> 16383
+    expect(Math.abs(view.getInt16(2, true) - 16383)).toBeLessThanOrEqual(1);
+    // 1.0 -> 32767
+    expect(view.getInt16(4, true)).toBe(0x7fff);
+    // 1.5 clamped to 1.0 -> 32767
+    expect(view.getInt16(6, true)).toBe(0x7fff);
+    // -0.5 -> -0.5 * 32768 = -16384
+    expect(Math.abs(view.getInt16(8, true) - -16384)).toBeLessThanOrEqual(1);
+    // -1.0 -> -32768
+    expect(view.getInt16(10, true)).toBe(-0x8000);
+    // -1.5 clamped to -1.0 -> -32768
+    expect(view.getInt16(12, true)).toBe(-0x8000);
+  });
+
+  test('encodeBase64 and decodeBase64 perform lossless roundtrip for arbitrary byte arrays', () => {
+    const rawBytes = new Uint8Array([0, 1, 255, 128, 42, 64, 18, 99, 127]);
+    const encoded = encodeBase64(rawBytes);
+    expect(typeof encoded).toBe('string');
+    expect(encoded.length).toBeGreaterThan(0);
+
+    const decoded = decodeBase64(encoded);
+    expect(decoded.length).toBe(rawBytes.length);
+    expect(Array.from(decoded)).toEqual(Array.from(rawBytes));
+  });
+
+  test('decodeAudioData converts raw PCM Int16 bytes into AudioBuffer channels', async () => {
+    // Construct mock AudioContext with createBuffer
+    const sampleRate = 24000;
+    const numChannels = 1;
+
+    const mockChannelData = new Float32Array(4);
+    const mockAudioBuffer = {
+      length: 4,
+      numberOfChannels: 1,
+      sampleRate,
+      getChannelData: () => mockChannelData
+    };
+
+    const mockCtx = {
+      createBuffer: (channels: number, length: number, rate: number) => {
+        expect(channels).toBe(1);
+        expect(length).toBe(4);
+        expect(rate).toBe(sampleRate);
+        return mockAudioBuffer;
+      }
+    } as unknown as AudioContext;
+
+    // 4 16-bit samples: 0, 32767, -32768, 16384
+    const int16Samples = new Int16Array([0, 32767, -32768, 16384]);
+    const byteData = new Uint8Array(int16Samples.buffer);
+
+    const result = await decodeAudioData(byteData, mockCtx, sampleRate, numChannels);
+    expect(result).toBe(mockAudioBuffer);
+
+    // Verify channel data normalized between -1.0 and 1.0
+    expect(mockChannelData[0]).toBe(0);
+    expect(mockChannelData[1]).toBeCloseTo(1.0, 2);
+    expect(mockChannelData[2]).toBe(-1.0);
+    expect(mockChannelData[3]).toBeCloseTo(0.5, 2);
+  });
+
+  test('decodeAudioData handles uneven byte lengths gracefully', async () => {
+    const mockChannelData = new Float32Array(2);
+    const mockAudioBuffer = {
+      length: 2,
+      numberOfChannels: 1,
+      sampleRate: 24000,
+      getChannelData: () => mockChannelData
+    };
+
+    const mockCtx = {
+      createBuffer: () => mockAudioBuffer
+    } as unknown as AudioContext;
+
+    // 5 bytes (uneven) -> trimmed to 4 bytes (2 samples)
+    const unevenBytes = new Uint8Array([0, 0, 255, 127, 42]);
+    const result = await decodeAudioData(unevenBytes, mockCtx);
+    expect(result).toBe(mockAudioBuffer);
+  });
+});