* i18n: complete internationalization for subagent orchestration page - Replace hardcoded English strings in [SubAgentPage.vue] with i18n keys. - Update `en-US` and `zh-CN` locales with missing hints, validation messages, and empty state translations. - Fix translation typos and improve consistency across the SubAgent orchestration UI. * fix(bug_risk): 避免在模板中的翻译调用上使用 || 'Close' 作为回退值。