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/pt.ts

@@ -151,6 +151,12 @@ export default {
     monitorRoleUser: 'Usuário',
     monitorRoleAssistant: 'Assistente',
     copySessionId: 'Copiar ID da sessão',
+    export: 'Exportar',
+    exportFull: 'Exportação completa (JSON)',
+    exportCompressed: 'Exportação comprimida (TXT)',
+    exportCompressing: 'Comprimindo contexto, aguarde...',
+    exportSuccess: 'Sessão exportada',
+    exportFailed: 'Falha ao exportar',
     renamed: 'Renomeado',
     renameFailed: 'Falha ao renomear',
     renameSession: 'Renomear sessao',