History gap after reconnect, ConversationsTab edition
As outlined (and fixed for MUCs in #3500 (closed)), there is a history gap when reconnecting to a private tab.
When I have an open ConversationTab, and poezio loses its connection, it will attempt a 0198 resume (if supported by the server). But sometimes, poezio was disconnected for so long that the 0198 hibernated session was killed and resumption fails, leading to holes in the perceived chat history.
When completing a reconnect, poezio should fetch MAM for all open ConversationTabs.