Schedule server message deletion

OpenIMConversationItem exposes Commercial isMsgDestruct and msgDestructTime state, but the current OpenIMSetConversationParams has no corresponding write fields.

Together, isMsgDestruct and msgDestructTime describe periodic server message deletion. This is not read-burn mode, which uses isPrivateChat and burnDuration.

This plugin release can read and display the server's destruction policy but cannot copy Wasm's setConversation({ isMsgDestruct, msgDestructTime }) call. Do not simulate the setter through a similar field or ex. Use a confirmed, authenticated commercial business API and requery the conversation after it completes.

When the interval is reached, server policy removes server-side stored messages. It does not promise that already synchronized local copies disappear immediately from this or another device. After reinstall, local-data clearing, or synchronization on a new device, messages already removed by the server may no longer be retrievable.

A client countdown is presentation only. Actual destruction is determined by Core and server state. This page preserves the same business boundary as Wasm while explicitly recording that the current Unix contract has no write capability.