会话状态监听

fun BimConversationService.addConversationStateListener(listener: BimConversationStateListener)
fun BimConversationService.removeConversationStateListener(listener: BimConversationStateListener)
fun BimConversationService.removeConversationStateListener(key: String)

val listener = object : BimConversationStateListener {
    override val key = "conversation_state_listener"

    override fun onDraftChanged(sessionId: String, draft: BimConversationDraft?) {}
    override fun onMentionsChanged(
        sessionId: String,
        mentions: List<BimConversationMention>,
    ) {}
}
BimImManager.getInstance().conversationService.addConversationStateListener(listener)

这是草稿和精确提及的独立回调边界，不会替代消息 listener，也不会直接修改消息列表。