refactor(main): IPC 채널 SSOT 일원화 + AppConfig 타입 강화 (WS2)

- ipc-channels.ts SSOT에 9개 그룹/키 추가: INSTRUCTION, SYSTEM_AUDIO,
  POPUP_RESULT/HISTORY/COMMAND/CAPTION, VOICE_PARTIAL, CLIPBOARD, APP,
  VOICE_CONVERSATION.FINISH_LISTENING
- WindowManager/handlers/bootstrap 하드코딩 채널 -> IPC_CHANNELS 교체.
  불일치 4건(result:* vs window:tip*)은 preload 재검증 후 SSOT로 통일.
  notifyRenderer channel: string -> IPCChannel 타입 좁힘.
- AppConfig에 7개 누락 키 추가(customInstructions, llmChains,
  voiceCommandRules, voiceCommandsEnabled, activeInstructionId,
  activeChainId, captionAudioSource) -> as never 16건 제거.
- ChainService/CustomInstructionService/WindowManager dynamic require -> static import.
- services/index.ts 데드 레지스트리 제거 (import 0건).
SKIP: ipcSuccess/ipcError 헬퍼 통일, catch 패턴(별도)
정책: docs/REFACTOR_POLICY.md DP2, DP9

apps/desktop/src/main/services/VoiceModeService.ts

@@ -752,7 +752,7 @@ class VoiceModeService extends EventEmitter {
       if (action === 'chain') {
         try {
           const { getChainService } = await import('./ChainService')
-          const activeChainId = configGet('activeChainId' as keyof import('@d3ro/core/types').AppConfig) as unknown as string
+          const activeChainId = configGet('activeChainId')
           if (activeChainId) {
             const chainResult = await getChainService().execute(activeChainId, contextPrefix + transcribedText)
             if (this._isInTerminalState()) return
@@ -769,7 +769,7 @@ class VoiceModeService extends EventEmitter {
 
       // 음성 단축키 오버라이드 또는 활성 명령어
       const effectiveInstructionId = overrideInstructionId
-        ?? (configGet('activeInstructionId' as keyof import('@d3ro/core/types').AppConfig) as unknown as string)
+        ?? configGet('activeInstructionId')
 
       if (action === 'custom' || overrideInstructionId) {
         let customPrompt = contextPrefix + transcribedText