feat: add session export with full and compressed modes (#507)

Add export functionality that allows users to download session data
as JSON or plain text, with optional LLM-based context compression
for long conversations. Includes UI controls in chat panel, session
list, and history view, plus i18n strings for all 8 locales.

Co-authored-by: Claude Opus 4.7 <noreply@anthropic.com>

packages/client/src/i18n/locales/ko.ts

@@ -151,6 +151,12 @@ export default {
     monitorRoleUser: '사용자',
     monitorRoleAssistant: '어시스턴트',
     copySessionId: '세션 ID 복사',
+    export: '내보내기',
+    exportFull: '전체 내보내기 (JSON)',
+    exportCompressed: '압축 내보내기 (TXT)',
+    exportCompressing: '컨텍스트 압축 중, 잠시 기다려주세요...',
+    exportSuccess: '세션을 내보냈습니다',
+    exportFailed: '내보내기 실패',
     renamed: '이름이 변경되었습니다',
     renameFailed: '이름 변경 실패',
     renameSession: '세션 이름 변경',