冲突解决：用户与状态模型
定义了一个三方冲突模型用于协作记录，保留基础版本、本地意图和当前远程状态，同时区分可合并字段与需要用户决策的不变量。
Offline edits carry stable operation identity; the server remains authoritative for conflicts, tombstones propagate deletes, and clients surface merge outcomes instead of silently dropping divergent local changes.