Agent Skills: lc-faq-add

File an interview question and answer into doc/faq/ in the shape the other 49 FAQs use — the sheet its Scope line owns, the numbered section it belongs under, tagged code fences — and write the matching 繁體中文 overlay section in the same pass, because that tree is 100% translated and a new English answer leaves a hole the moment it lands. Use when asked to add an FAQ entry, document an interview question, answer a backend/Java/SQL/Kafka question into the notes, or start a new FAQ file. Triggers - "add a question about virtual threads to the java FAQ", "/lc-faq-add kafka rebalancing", "document this interview question", "start a FAQ for gRPC".