im (v1)

CRITICAL — 开始前 MUST 先用 Read 工具读取 ../lark-shared/SKILL.md，其中包含认证、权限处理

Core Concepts

Message: A single message in a chat, identified by message_id (om_xxx). Supports types: text, post, image, file, audio, video, sticker, interactive (card), share_chat, share_user, merge_forward, etc.
Chat: A group chat or P2P conversation, identified by chat_id (oc_xxx).
Thread: A reply thread under a message, identified by thread_id (om_xxx or omt_xxx).
Reaction: An emoji reaction on a message.
Flag: A bookmark on a message or thread.
Feed Shortcut: A chat pinned to the current user's feed sidebar, identified by feed_card_id (an oc_xxx open_chat_id for CHAT type).
Feed Group: A tag that groups feed cards in the feed list, identified by feed_group_id (ofg_xxx). Members are feed cards, each identified by feed_id + feed_type. Two types: normal (members managed explicitly) and rule (members auto-derived from rules).