Phase 9: About 탭 + 녹음 오디오 WAV 저장

- Settings: 정보(About) 탭 추가 (버전, 기술 스택, 음성 엔진 정보)
- VoiceModeService: 전사 완료 시 PCM→WAV 파일 저장 ({userData}/recordings/)
  - WAV 헤더 생성 (16kHz, 16bit, mono)
  - HistoryService와 연동 가능 (audioLocalPath)
- docs/phases/phase-9.md 설계 문서 작성

src/main/services/VoiceModeService.ts

@@ -5,6 +5,9 @@
 
 import { EventEmitter } from 'events'
 import { randomUUID } from 'crypto'
+import { writeFile, mkdir } from 'fs/promises'
+import { join } from 'path'
+import { app } from 'electron'
 import { getLogger } from './LoggerService'
 import { getAudioCaptureService } from './AudioCaptureService'
 import { getLocalSTTService } from './LocalSTTService'
@@ -97,6 +100,9 @@ class VoiceModeService extends EventEmitter {
   private _audioBuffer: Buffer[] = []
   private _audioBufferBytes = 0
 
+  // 녹음 오디오 저장용
+  private _lastAudioBuffer: Buffer | null = null
+
   // 에러 가드
   private _errorEmitted = false
 
@@ -404,6 +410,7 @@ class VoiceModeService extends EventEmitter {
     this._setRecognitionState(RecognitionState.RECOGNIZING)
 
     const merged = Buffer.concat(this._audioBuffer)
+    this._lastAudioBuffer = merged // WAV 저장용 복사본
     this._audioBuffer = []
     this._audioBufferBytes = 0
 
@@ -497,6 +504,48 @@ class VoiceModeService extends EventEmitter {
         showResultPopup(finalText, 10000)
       }
     }
+
+    // 녹음 오디오 WAV 파일 저장 (비동기, 실패해도 무시)
+    this._saveAudioFile(session.id)
+  }
+
+  /** PCM 버퍼를 WAV 파일로 저장 */
+  private async _saveAudioFile(sessionId: string): Promise<void> {
+    if (!this._lastAudioBuffer || this._lastAudioBuffer.length === 0) return
+
+    try {
+      const recordingsDir = join(app.getPath('userData'), 'recordings')
+      await mkdir(recordingsDir, { recursive: true })
+
+      const wavPath = join(recordingsDir, `${sessionId}.wav`)
+      const pcmData = this._lastAudioBuffer
+
+      // WAV 헤더 생성 (16kHz, 16bit, mono)
+      const header = Buffer.alloc(44)
+      const dataSize = pcmData.length
+      const fileSize = dataSize + 36
+
+      header.write('RIFF', 0)
+      header.writeUInt32LE(fileSize, 4)
+      header.write('WAVE', 8)
+      header.write('fmt ', 12)
+      header.writeUInt32LE(16, 16) // fmt chunk size
+      header.writeUInt16LE(1, 20) // PCM format
+      header.writeUInt16LE(1, 22) // mono
+      header.writeUInt32LE(16000, 24) // sample rate
+      header.writeUInt32LE(32000, 28) // byte rate (16000 * 2)
+      header.writeUInt16LE(2, 32) // block align
+      header.writeUInt16LE(16, 34) // bits per sample
+      header.write('data', 36)
+      header.writeUInt32LE(dataSize, 40)
+
+      await writeFile(wavPath, Buffer.concat([header, pcmData]))
+      logger.info(`Audio saved: ${wavPath} (${Math.round(dataSize / 1024)}KB)`)
+    } catch (error) {
+      logger.warn(`Audio save failed: ${error instanceof Error ? error.message : String(error)}`)
+    } finally {
+      this._lastAudioBuffer = null
+    }
   }
 
   private _cancelSession(reason: 'user' | 'timeout' | 'too-short'): void {